/usr/share/debian-reference/ch05.en.html is in debian-reference-en 2.68.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835 836 837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879 880 881 882 883 884 885 886 887 888 889 890 891 892 893 894 895 896 897 898 899 900 901 902 903 904 905 906 907 908 909 910 911 912 913 914 915 916 917 918 919 920 921 922 923 924 925 926 927 928 929 930 931 932 933 934 935 936 937 938 939 940 941 942 943 944 945 946 947 948 949 950 951 952 953 954 955 956 957 958 959 960 961 962 963 964 965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 980 981 982 983 984 985 986 987 988 989 990 991 992 993 994 995 996 997 998 999 1000 1001 1002 1003 1004 1005 1006 1007 1008 1009 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027 1028 1029 1030 1031 1032 1033 1034 1035 1036 1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 1047 1048 1049 1050 1051 1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063 1064 1065 1066 1067 1068 1069 1070 1071 1072 1073 1074 1075 1076 1077 1078 1079 1080 1081 1082 1083 1084 1085 1086 1087 1088 1089 1090 1091 1092 1093 1094 1095 1096 1097 1098 1099 1100 1101 1102 1103 1104 1105 1106 1107 1108 1109 1110 1111 1112 1113 1114 1115 1116 1117 1118 1119 1120 1121 1122 1123 1124 1125 1126 1127 1128 1129 1130 1131 1132 1133 1134 1135 1136 1137 1138 1139 1140 1141 1142 1143 1144 1145 1146 1147 1148 1149 1150 1151 1152 1153 1154 1155 1156 1157 1158 1159 1160 1161 1162 1163 1164 1165 1166 1167 1168 1169 1170 1171 1172 1173 1174 1175 1176 1177 1178 1179 1180 1181 1182 1183 1184 1185 1186 1187 1188 1189 1190 1191 1192 1193 1194 1195 1196 1197 1198 1199 1200 1201 1202 1203 1204 1205 1206 1207 1208 1209 1210 1211 1212 1213 1214 1215 1216 1217 1218 1219 1220 1221 1222 1223 1224 1225 1226 1227 1228 1229 1230 1231 1232 1233 1234 1235 1236 1237 1238 1239 1240 1241 1242 1243 1244 1245 1246 1247 1248 1249 1250 1251 1252 1253 1254 1255 1256 1257 1258 1259 1260 1261 1262 1263 1264 1265 1266 1267 1268 1269 1270 1271 1272 1273 1274 1275 1276 1277 1278 1279 1280 1281 1282 1283 1284 1285 1286 1287 1288 1289 1290 1291 1292 1293 1294 1295 1296 1297 1298 1299 1300 1301 1302 1303 1304 1305 1306 1307 1308 1309 1310 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 1321 1322 1323 1324 1325 1326 1327 1328 1329 1330 1331 1332 1333 1334 1335 1336 1337 1338 1339 1340 1341 1342 1343 1344 1345 1346 1347 1348 1349 1350 1351 1352 1353 1354 1355 1356 1357 1358 1359 1360 1361 1362 1363 1364 1365 1366 1367 1368 1369 1370 1371 1372 1373 1374 1375 1376 1377 1378 1379 1380 1381 1382 1383 1384 1385 1386 1387 1388 1389 1390 1391 1392 1393 1394 1395 1396 1397 1398 1399 1400 1401 1402 1403 1404 1405 1406 1407 1408 1409 1410 1411 1412 1413 1414 1415 1416 1417 1418 1419 1420 1421 1422 1423 1424 1425 1426 1427 1428 1429 1430 1431 1432 1433 1434 1435 1436 1437 1438 1439 1440 1441 1442 1443 1444 1445 1446 1447 1448 1449 1450 1451 1452 1453 1454 1455 1456 1457 1458 1459 1460 1461 1462 1463 1464 1465 1466 1467 1468 1469 1470 1471 1472 1473 1474 1475 1476 1477 1478 1479 1480 1481 1482 1483 1484 1485 1486 1487 1488 1489 1490 1491 1492 1493 1494 1495 1496 1497 1498 1499 1500 1501 1502 1503 1504 1505 1506 1507 1508 1509 1510 1511 1512 1513 1514 1515 1516 1517 1518 1519 1520 1521 1522 1523 1524 1525 1526 1527 1528 1529 1530 1531 1532 1533 1534 1535 1536 1537 1538 1539 1540 1541 1542 1543 1544 1545 1546 1547 1548 1549 1550 1551 1552 1553 1554 1555 1556 1557 1558 1559 1560 1561 1562 1563 1564 1565 1566 1567 1568 1569 1570 1571 1572 1573 1574 1575 1576 1577 1578 1579 1580 1581 1582 1583 1584 1585 1586 1587 1588 1589 1590 1591 1592 1593 1594 1595 1596 1597 1598 1599 1600 1601 1602 1603 1604 1605 1606 1607 1608 1609 1610 1611 1612 1613 1614 1615 1616 1617 1618 1619 1620 1621 1622 1623 1624 1625 1626 1627 1628 1629 1630 1631 1632 1633 1634 1635 1636 1637 1638 1639 1640 1641 1642 1643 1644 1645 1646 1647 1648 1649 1650 1651 1652 1653 1654 1655 1656 1657 1658 1659 1660 1661 1662 1663 1664 1665 1666 1667 1668 1669 1670 1671 1672 1673 1674 1675 1676 1677 1678 1679 1680 1681 1682 1683 1684 1685 1686 1687 1688 1689 1690 1691 1692 1693 1694 1695 1696 1697 1698 1699 1700 1701 1702 1703 1704 1705 1706 1707 1708 1709 1710 1711 1712 1713 1714 1715 1716 1717 1718 1719 1720 1721 1722 1723 1724 1725 1726 1727 1728 1729 1730 1731 1732 1733 1734 1735 1736 1737 1738 1739 1740 1741 1742 1743 1744 1745 1746 1747 1748 1749 1750 1751 1752 1753 1754 1755 1756 1757 1758 1759 1760 1761 1762 1763 1764 1765 1766 1767 1768 1769 1770 1771 1772 1773 1774 1775 1776 1777 1778 1779 1780 1781 1782 1783 1784 1785 1786 1787 1788 1789 1790 1791 1792 1793 1794 1795 1796 1797 1798 1799 1800 1801 1802 1803 1804 1805 1806 1807 1808 1809 1810 1811 1812 1813 1814 1815 1816 1817 1818 1819 1820 1821 1822 1823 1824 1825 1826 1827 1828 1829 1830 1831 1832 1833 1834 1835 1836 1837 1838 1839 1840 1841 1842 1843 1844 1845 1846 1847 1848 1849 1850 1851 1852 1853 1854 1855 1856 1857 1858 1859 1860 1861 1862 1863 1864 1865 1866 1867 1868 1869 1870 1871 1872 1873 1874 1875 1876 1877 1878 1879 1880 1881 1882 1883 1884 1885 1886 1887 1888 1889 1890 1891 1892 1893 1894 1895 1896 1897 1898 1899 1900 1901 1902 1903 1904 1905 1906 1907 1908 1909 1910 1911 1912 1913 1914 1915 1916 1917 1918 1919 1920 1921 1922 1923 1924 1925 1926 1927 1928 1929 1930 1931 1932 1933 1934 1935 1936 1937 1938 1939 1940 1941 1942 1943 1944 1945 1946 1947 1948 1949 1950 1951 1952 1953 1954 1955 1956 1957 1958 1959 1960 1961 1962 1963 1964 1965 1966 1967 1968 1969 1970 1971 1972 1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024 2025 2026 2027 2028 2029 2030 2031 2032 2033 2034 2035 2036 2037 2038 2039 2040 2041 2042 2043 2044 2045 2046 2047 2048 2049 2050 2051 2052 2053 2054 2055 2056 2057 2058 2059 2060 2061 2062 2063 2064 2065 2066 2067 2068 2069 2070 2071 2072 2073 2074 2075 2076 2077 2078 2079 2080 2081 2082 2083 2084 2085 2086 2087 2088 2089 2090 2091 2092 2093 2094 2095 2096 2097 2098 2099 2100 2101 2102 2103 2104 2105 2106 2107 2108 2109 2110 2111 2112 2113 2114 2115 2116 2117 2118 2119 2120 2121 2122 2123 2124 2125 2126 2127 2128 2129 2130 2131 2132 2133 2134 2135 2136 2137 2138 2139 2140 2141 2142 2143 2144 2145 2146 2147 2148 2149 2150 2151 2152 2153 2154 2155 2156 2157 2158 2159 2160 2161 2162 2163 2164 2165 2166 2167 2168 2169 2170 2171 2172 2173 2174 2175 2176 2177 2178 2179 2180 2181 2182 2183 2184 2185 2186 2187 2188 2189 2190 2191 2192 2193 2194 2195 2196 2197 2198 2199 2200 2201 2202 2203 2204 2205 2206 2207 2208 2209 2210 2211 2212 2213 2214 2215 2216 2217 2218 2219 2220 2221 2222 2223 2224 2225 2226 2227 2228 2229 2230 2231 2232 2233 2234 2235 2236 2237 2238 2239 2240 2241 2242 2243 2244 2245 2246 2247 2248 2249 2250 2251 2252 2253 2254 2255 2256 2257 2258 2259 2260 2261 2262 2263 2264 2265 2266 2267 2268 2269 2270 2271 2272 2273 2274 2275 2276 2277 2278 2279 2280 2281 2282 2283 2284 2285 2286 2287 2288 2289 2290 2291 2292 2293 2294 2295 2296 2297 2298 2299 2300 2301 2302 2303 2304 2305 2306 2307 2308 2309 2310 2311 2312 2313 2314 2315 2316 2317 2318 2319 2320 2321 2322 2323 2324 2325 2326 2327 2328 2329 2330 2331 2332 2333 2334 2335 2336 2337 2338 2339 2340 2341 2342 2343 2344 2345 2346 2347 2348 2349 2350 2351 2352 2353 2354 2355 2356 2357 2358 2359 2360 2361 2362 2363 2364 2365 2366 2367 2368 2369 2370 2371 2372 2373 2374 2375 2376 2377 2378 2379 2380 2381 2382 2383 2384 2385 2386 2387 2388 2389 2390 2391 2392 2393 2394 2395 2396 2397 2398 2399 2400 2401 2402 2403 2404 2405 2406 2407 2408 2409 2410 2411 2412 2413 2414 2415 2416 2417 2418 2419 2420 2421 2422 2423 2424 2425 2426 2427 2428 2429 2430 2431 2432 2433 2434 2435 2436 2437 2438 2439 2440 2441 2442 2443 2444 2445 2446 2447 2448 2449 2450 2451 2452 2453 2454 2455 2456 2457 2458 2459 2460 2461 2462 2463 2464 2465 2466 2467 2468 2469 2470 2471 2472 2473 2474 2475 2476 2477 2478 2479 2480 2481 2482 2483 2484 2485 2486 2487 2488 2489 2490 2491 2492 2493 2494 2495 2496 2497 2498 2499 2500 2501 2502 2503 2504 2505 2506 2507 2508 2509 2510 2511 2512 2513 2514 2515 2516 2517 2518 2519 2520 2521 2522 2523 2524 2525 2526 2527 2528 2529 2530 2531 2532 2533 2534 2535 2536 2537 2538 2539 2540 2541 2542 2543 2544 2545 2546 2547 2548 2549 2550 2551 2552 2553 2554 2555 2556 2557 2558 2559 2560 2561 2562 2563 2564 2565 2566 2567 2568 2569 2570 2571 2572 2573 2574 2575 2576 2577 2578 2579 2580 2581 2582 2583 2584 2585 2586 2587 2588 2589 2590 2591 2592 2593 2594 2595 2596 2597 2598 2599 2600 2601 2602 2603 2604 2605 2606 2607 2608 2609 2610 2611 2612 2613 2614 2615 2616 2617 2618 2619 2620 2621 2622 2623 2624 2625 2626 2627 2628 2629 2630 2631 2632 2633 2634 2635 2636 2637 2638 2639 2640 2641 2642 2643 2644 2645 2646 2647 2648 2649 2650 2651 2652 2653 2654 2655 2656 2657 2658 2659 2660 2661 2662 2663 2664 2665 2666 2667 2668 2669 2670 2671 2672 2673 2674 2675 2676 2677 2678 2679 2680 2681 2682 2683 2684 2685 2686 2687 2688 2689 2690 2691 2692 2693 2694 2695 2696 2697 2698 2699 2700 2701 2702 2703 2704 2705 2706 2707 2708 2709 2710 2711 2712 2713 2714 2715 2716 2717 2718 2719 2720 2721 2722 2723 2724 2725 2726 2727 2728 2729 2730 2731 2732 2733 2734 2735 2736 2737 2738 2739 2740 2741 2742 2743 2744 2745 2746 2747 2748 2749 2750 2751 2752 2753 2754 2755 2756 2757 2758 2759 2760 2761 2762 2763 2764 2765 2766 2767 2768 2769 2770 2771 2772 2773 2774 2775 2776 2777 2778 2779 2780 2781 2782 2783 2784 2785 2786 2787 2788 2789 2790 2791 2792 2793 2794 2795 2796 2797 2798 2799 2800 2801 2802 2803 2804 2805 2806 2807 2808 2809 2810 2811 2812 2813 2814 2815 2816 2817 2818 2819 2820 2821 2822 2823 2824 2825 2826 2827 2828 2829 2830 2831 2832 2833 2834 2835 2836 2837 2838 2839 2840 2841 2842 2843 2844 2845 2846 2847 2848 2849 2850 2851 2852 2853 2854 2855 2856 2857 2858 2859 2860 2861 2862 2863 2864 2865 2866 2867 2868 2869 2870 2871 2872 2873 2874 2875 2876 2877 2878 2879 2880 2881 2882 2883 2884 2885 2886 2887 2888 2889 2890 2891 2892 2893 2894 2895 2896 2897 2898 2899 2900 2901 2902 2903 2904 2905 2906 2907 2908 2909 2910 2911 2912 2913 2914 2915 2916 2917 2918 2919 2920 2921 2922 2923 2924 2925 2926 2927 2928 2929 2930 2931 2932 2933 2934 2935 2936 2937 2938 2939 2940 2941 2942 2943 2944 2945 2946 2947 2948 2949 2950 2951 2952 2953 2954 2955 2956 2957 2958 2959 2960 2961 2962 2963 2964 2965 2966 2967 2968 2969 2970 2971 2972 2973 2974 2975 2976 2977 2978 2979 2980 2981 2982 2983 2984 2985 2986 2987 2988 2989 2990 2991 2992 2993 2994 2995 2996 2997 2998 2999 3000 3001 3002 3003 3004 3005 3006 3007 3008 3009 3010 3011 3012 3013 3014 3015 3016 3017 3018 3019 3020 3021 3022 3023 3024 3025 3026 3027 3028 3029 3030 3031 3032 3033 3034 3035 3036 3037 3038 3039 3040 3041 3042 3043 3044 3045 3046 3047 3048 3049 3050 3051 3052 3053 3054 3055 3056 3057 3058 3059 3060 3061 3062 3063 3064 3065 3066 3067 3068 3069 3070 3071 3072 3073 3074 3075 3076 3077 3078 3079 3080 3081 3082 3083 3084 3085 3086 3087 3088 3089 3090 3091 3092 3093 3094 3095 3096 3097 3098 3099 3100 3101 3102 3103 3104 3105 3106 3107 3108 3109 3110 3111 3112 3113 3114 3115 3116 3117 3118 3119 3120 3121 3122 3123 3124 3125 3126 3127 3128 3129 3130 3131 3132 3133 3134 3135 3136 3137 3138 3139 3140 3141 3142 3143 3144 3145 3146 3147 3148 3149 3150 3151 3152 3153 3154 3155 3156 3157 3158 3159 3160 3161 3162 3163 3164 3165 3166 3167 3168 3169 3170 3171 3172 3173 3174 3175 3176 3177 3178 3179 3180 3181 3182 3183 3184 3185 3186 3187 3188 3189 3190 3191 3192 3193 3194 3195 3196 3197 3198 3199 3200 3201 3202 3203 3204 3205 3206 3207 3208 3209 3210 3211 3212 3213 3214 3215 3216 3217 3218 3219 3220 3221 3222 3223 3224 3225 3226 3227 3228 3229 3230 3231 3232 3233 3234 3235 3236 3237 3238 3239 3240 3241 3242 3243 3244 3245 3246 3247 3248 3249 3250 3251 3252 3253 3254 3255 3256 3257 3258 3259 3260 3261 3262 3263 3264 3265 3266 3267 3268 3269 3270 3271 3272 3273 3274 3275 3276 3277 3278 3279 3280 3281 3282 3283 3284 3285 3286 3287 3288 3289 3290 3291 3292 3293 3294 3295 3296 3297 3298 3299 3300 3301 3302 3303 3304 3305 3306 3307 3308 3309 3310 3311 3312 3313 3314 3315 3316 3317 3318 3319 3320 3321 3322 3323 3324 3325 3326 3327 3328 3329 3330 3331 3332 3333 3334 3335 3336 3337 3338 3339 3340 3341 3342 3343 3344 3345 3346 3347 3348 3349 3350 3351 3352 3353 3354 3355 3356 3357 3358 3359 3360 3361 3362 3363 3364 3365 3366 3367 3368 3369 3370 3371 3372 3373 3374 3375 3376 3377 3378 3379 3380 3381 3382 3383 3384 3385 3386 3387 3388 3389 3390 3391 3392 3393 3394 3395 3396 3397 3398 3399 3400 3401 3402 3403 3404 3405 3406 3407 3408 3409 3410 3411 3412 3413 3414 3415 3416 3417 3418 3419 3420 3421 3422 3423 3424 3425 3426 3427 3428 3429 3430 3431 3432 3433 3434 3435 3436 3437 3438 3439 3440 3441 3442 3443 3444 3445 3446 3447 3448 3449 3450 3451 3452 3453 3454 3455 3456 3457 3458 3459 3460 3461 3462 3463 3464 3465 3466 3467 3468 3469 3470 3471 3472 3473 3474 3475 3476 3477 3478 3479 3480 3481 3482 3483 3484 3485 3486 3487 3488 3489 3490 3491 3492 3493 3494 3495 3496 3497 3498 3499 3500 3501 3502 3503 3504 3505 3506 3507 3508 3509 3510 3511 3512 3513 3514 3515 3516 3517 3518 3519 3520 3521 3522 3523 3524 3525 3526 3527 3528 3529 3530 3531 3532 3533 3534 3535 3536 3537 3538 3539 3540 3541 3542 3543 3544 3545 3546 3547 3548 3549 3550 3551 3552 3553 3554 3555 3556 3557 3558 3559 3560 3561 3562 3563 3564 3565 3566 3567 3568 3569 3570 3571 3572 3573 3574 3575 3576 3577 3578 3579 3580 3581 3582 3583 3584 3585 3586 3587 3588 3589 3590 3591 3592 3593 3594 3595 3596 3597 3598 3599 3600 3601 3602 3603 3604 3605 3606 3607 3608 3609 3610 3611 3612 3613 3614 3615 3616 3617 3618 3619 3620 3621 3622 3623 3624 3625 3626 3627 3628 3629 3630 3631 3632 3633 3634 3635 3636 3637 3638 3639 3640 3641 3642 3643 3644 3645 3646 3647 3648 3649 3650 3651 3652 3653 3654 3655 3656 3657 3658 3659 3660 3661 3662 3663 3664 3665 3666 3667 3668 3669 3670 3671 3672 3673 3674 3675 3676 3677 3678 3679 3680 3681 3682 3683 3684 3685 3686 3687 3688 3689 3690 3691 3692 3693 3694 3695 3696 3697 3698 3699 3700 3701 3702 3703 3704 3705 3706 3707 3708 3709 3710 3711 3712 3713 3714 3715 3716 3717 3718 3719 3720 3721 3722 3723 3724 3725 3726 3727 3728 3729 3730 3731 3732 3733 3734 3735 3736 3737 3738 3739 3740 3741 3742 3743 3744 3745 3746 3747 3748 3749 3750 3751 3752 3753 3754 3755 3756 3757 3758 3759 3760 3761 3762 3763 3764 3765 3766 3767 3768 3769 3770 3771 3772 3773 3774 3775 3776 3777 3778 3779 3780 3781 3782 3783 3784 3785 3786 3787 3788 3789 3790 3791 3792 3793 3794 3795 3796 3797 3798 3799 3800 3801 3802 3803 3804 3805 3806 3807 3808 3809 3810 3811 3812 3813 3814 3815 3816 3817 3818 3819 3820 3821 3822 3823 3824 3825 3826 3827 3828 3829 3830 3831 3832 3833 3834 3835 3836 3837 3838 3839 3840 3841 3842 3843 3844 3845 3846 3847 3848 3849 3850 3851 3852 3853 3854 3855 3856 3857 3858 3859 3860 3861 3862 3863 3864 3865 3866 3867 3868 3869 3870 3871 3872 3873 3874 3875 3876 3877 3878 3879 3880 3881 3882 3883 3884 3885 3886 3887 3888 3889 3890 3891 3892 3893 3894 3895 3896 3897 3898 3899 3900 3901 3902 3903 3904 3905 3906 3907 3908 3909 3910 3911 3912 3913 3914 3915 3916 3917 3918 3919 3920 3921 3922 3923 3924 3925 3926 3927 3928 3929 3930 3931 3932 3933 3934 3935 3936 3937 3938 3939 3940 3941 3942 3943 3944 3945 3946 3947 3948 3949 3950 3951 3952 3953 3954 3955 3956 3957 3958 3959 3960 3961 3962 3963 3964 3965 3966 3967 3968 3969 3970 3971 3972 3973 3974 3975 3976 3977 3978 3979 3980 3981 3982 3983 3984 3985 3986 3987 3988 3989 3990 3991 3992 3993 3994 3995 3996 3997 3998 3999 4000 4001 4002 4003 4004 4005 4006 4007 4008 4009 4010 4011 4012 4013 4014 4015 4016 4017 4018 4019 4020 4021 4022 4023 4024 4025 4026 4027 4028 4029 4030 4031 4032 4033 4034 4035 4036 4037 4038 4039 4040 4041 4042 4043 4044 4045 4046 4047 4048 4049 4050 4051 4052 4053 4054 4055 4056 4057 4058 4059 4060 4061 4062 4063 4064 4065 4066 4067 4068 4069 4070 4071 4072 4073 4074 4075 4076 4077 4078 4079 4080 4081 4082 4083 4084 4085 4086 4087 4088 4089 4090 4091 4092 4093 4094 4095 4096 4097 4098 4099 4100 4101 4102 4103 4104 4105 4106 4107 4108 4109 4110 4111 4112 4113 4114 4115 4116 4117 4118 4119 4120 4121 4122 4123 4124 4125 4126 4127 4128 4129 4130 4131 4132 4133 4134 4135 4136 4137 4138 4139 4140 4141 4142 4143 4144 4145 4146 4147 4148 4149 4150 4151 4152 4153 4154 4155 4156 4157 4158 4159 4160 4161 4162 4163 4164 4165 4166 4167 4168 4169 4170 4171 4172 4173 4174 4175 4176 4177 4178 4179 4180 4181 4182 4183 4184 4185 4186 4187 4188 4189 4190 4191 4192 4193 4194 4195 4196 4197 4198 4199 4200 4201 4202 4203 4204 4205 4206 4207 4208 4209 4210 4211 4212 4213 4214 4215 4216 4217 4218 4219 4220 4221 4222 4223 4224 4225 4226 4227 4228 4229 4230 4231 4232 4233 4234 4235 4236 4237 4238 4239 4240 4241 4242 4243 4244 4245 4246 4247 4248 4249 4250 4251 4252 4253 4254 4255 4256 4257 4258 4259 4260 4261 4262 4263 4264 4265 4266 4267 4268 4269 4270 4271 4272 4273 4274 4275 4276 4277 4278 4279 4280 4281 4282 4283 4284 4285 4286 4287 4288 4289 4290 4291 4292 4293 4294 4295 4296 4297 4298 4299 4300 4301 4302 4303 4304 4305 4306 4307 4308 4309 4310 4311 4312 4313 4314 4315 4316 4317 4318 4319 4320 4321 4322 4323 4324 4325 4326 4327 4328 4329 4330 4331 4332 4333 4334 4335 4336 4337 4338 4339 4340 4341 4342 4343 4344 4345 4346 4347 4348 4349 4350 4351 4352 4353 4354 4355 4356 4357 4358 4359 4360 4361 4362 4363 4364 4365 4366 4367 4368 4369 4370 4371 4372 4373 4374 4375 4376 4377 4378 4379 4380 4381 4382 4383 4384 4385 4386 4387 4388 4389 4390 4391 4392 4393 4394 4395 4396 4397 4398 4399 4400 4401 4402 4403 4404 4405 4406 4407 4408 4409 4410 4411 4412 4413 4414 4415 4416 4417 4418 4419 4420 4421 4422 4423 4424 4425 4426 4427 4428 4429 4430 4431 4432 4433 4434 4435 4436 4437 4438 4439 4440 4441 4442 4443 4444 4445 4446 4447 4448 4449 4450 4451 4452 4453 4454 4455 4456 4457 4458 4459 4460 4461 4462 4463 4464 4465 4466 4467 4468 4469 4470 4471 4472 4473 4474 4475 4476 4477 4478 4479 4480 4481 4482 4483 4484 4485 4486 4487 4488 4489 4490 4491 4492 4493 4494 4495 4496 4497 4498 4499 4500 4501 4502 4503 4504 4505 4506 4507 4508 4509 4510 4511 4512 4513 4514 4515 4516 4517 4518 4519 4520 4521 4522 4523 4524 4525 4526 4527 4528 4529 4530 4531 4532 4533 4534 4535 4536 4537 4538 4539 4540 4541 4542 4543 4544 4545 4546 4547 4548 4549 4550 4551 4552 4553 4554 4555 4556 4557 4558 4559 4560 4561 4562 4563 4564 4565 4566 4567 4568 4569 4570 4571 4572 4573 4574 4575 4576 4577 4578 4579 4580 4581 4582 4583 4584 4585 4586 4587 4588 4589 4590 4591 4592 4593 4594 4595 4596 4597 4598 4599 4600 4601 4602 4603 4604 4605 4606 4607 4608 4609 4610 4611 4612 4613 4614 4615 4616 4617 4618 4619 4620 4621 4622 4623 4624 4625 4626 4627 4628 4629 4630 4631 4632 4633 4634 4635 4636 4637 4638 4639 4640 4641 4642 4643 4644 4645 4646 4647 4648 4649 4650 4651 4652 4653 4654 4655 4656 4657 4658 4659 4660 4661 4662 4663 4664 4665 4666 4667 4668 4669 4670 4671 4672 4673 4674 4675 4676 4677 4678 4679 4680 4681 4682 4683 4684 4685 4686 4687 4688 4689 4690 4691 4692 4693 4694 4695 4696 4697 4698 4699 4700 4701 4702 4703 4704 4705 4706 4707 4708 4709 4710 4711 4712 4713 4714 | <?xml version="1.0" encoding="UTF-8" standalone="no"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>Chapter 5. Network setup</title>
<link rel="stylesheet" type="text/css" href="debian-reference.css"/>
<meta name="generator" content="DocBook XSL Stylesheets V1.79.1"/>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"/>
<link rel="home" href="index.en.html" title="Debian Reference"/>
<link rel="up" href="index.en.html" title="Debian Reference"/>
<link rel="prev" href="ch04.en.html" title="Chapter 4. Authentication"/>
<link rel="next" href="ch06.en.html" title="Chapter 6. Network applications"/>
</head>
<body>
<div class="navheader">
<table width="100%" summary="Navigation header">
<tr>
<th colspan="3" align="center">Chapter 5. Network setup</th>
</tr>
<tr>
<td align="left"><a accesskey="p" href="ch04.en.html"><img src="images/prev.png" alt="Prev"/></a> </td>
<th width="60%" align="center"> </th>
<td align="right"> <a accesskey="n" href="ch06.en.html"><img src="images/next.png" alt="Next"/></a></td>
</tr>
</table>
<hr/>
</div>
<div class="chapter">
<div class="titlepage">
<div>
<div>
<h1 class="title"><a id="_network_setup"/>Chapter 5. Network setup</h1>
</div>
</div>
</div>
<div class="toc">
<p>
<strong>Table of Contents</strong>
</p>
<dl class="toc">
<dt>
<span class="section">
<a href="ch05.en.html#_the_basic_network_infrastructure">5.1. The basic network infrastructure</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="ch05.en.html#_the_hostname_resolution">5.1.1. The hostname resolution</a>
</span>
</dt>
<dt>
<span class="section">
<a href="ch05.en.html#_the_network_interface_name">5.1.2. The network interface name</a>
</span>
</dt>
<dt>
<span class="section">
<a href="ch05.en.html#_the_network_address_range_for_the_lan">5.1.3. The network address range for the LAN</a>
</span>
</dt>
<dt>
<span class="section">
<a href="ch05.en.html#_the_network_device_support">5.1.4. The network device support</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="ch05.en.html#_the_modern_network_configuration_for_desktop">5.2. The modern network configuration for desktop</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="ch05.en.html#_gui_network_configuration_tools">5.2.1. GUI network configuration tools</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="ch05.en.html#_the_legacy_network_connection_and_configuration">5.3. The legacy network connection and configuration</a>
</span>
</dt>
<dt>
<span class="section">
<a href="ch05.en.html#_the_network_connection_method_legacy">5.4. The network connection method (legacy)</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="ch05.en.html#_the_dhcp_connection_with_the_ethernet">5.4.1. The DHCP connection with the Ethernet</a>
</span>
</dt>
<dt>
<span class="section">
<a href="ch05.en.html#_the_static_ip_connection_with_the_ethernet">5.4.2. The static IP connection with the Ethernet</a>
</span>
</dt>
<dt>
<span class="section">
<a href="ch05.en.html#_the_ppp_connection_with_pppconfig">5.4.3. The PPP connection with pppconfig</a>
</span>
</dt>
<dt>
<span class="section">
<a href="ch05.en.html#_the_alternative_ppp_connection_with_wvdialconf">5.4.4. The alternative PPP connection with wvdialconf</a>
</span>
</dt>
<dt>
<span class="section">
<a href="ch05.en.html#_the_pppoe_connection_with_pppoeconf">5.4.5. The PPPoE connection with pppoeconf</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="ch05.en.html#_the_basic_network_configuration_with_ifupdown_legacy">5.5. The basic network configuration with ifupdown (legacy)</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="ch05.en.html#_the_command_syntax_simplified">5.5.1. The command syntax simplified</a>
</span>
</dt>
<dt>
<span class="section">
<a href="ch05.en.html#_the_basic_syntax_of_etc_network_interfaces">5.5.2. The basic syntax of "/etc/network/interfaces"</a>
</span>
</dt>
<dt>
<span class="section">
<a href="ch05.en.html#_the_loopback_network_interface">5.5.3. The loopback network interface</a>
</span>
</dt>
<dt>
<span class="section">
<a href="ch05.en.html#_the_network_interface_served_by_the_dhcp">5.5.4. The network interface served by the DHCP</a>
</span>
</dt>
<dt>
<span class="section">
<a href="ch05.en.html#_the_network_interface_with_the_static_ip">5.5.5. The network interface with the static IP</a>
</span>
</dt>
<dt>
<span class="section">
<a href="ch05.en.html#_the_basics_of_wireless_lan_interface">5.5.6. The basics of wireless LAN interface</a>
</span>
</dt>
<dt>
<span class="section">
<a href="ch05.en.html#_the_wireless_lan_interface_with_wpa_wpa2">5.5.7. The wireless LAN interface with WPA/WPA2</a>
</span>
</dt>
<dt>
<span class="section">
<a href="ch05.en.html#_the_wireless_lan_interface_with_wep">5.5.8. The wireless LAN interface with WEP</a>
</span>
</dt>
<dt>
<span class="section">
<a href="ch05.en.html#_the_ppp_connection">5.5.9. The PPP connection</a>
</span>
</dt>
<dt>
<span class="section">
<a href="ch05.en.html#_the_alternative_ppp_connection">5.5.10. The alternative PPP connection</a>
</span>
</dt>
<dt>
<span class="section">
<a href="ch05.en.html#_the_pppoe_connection">5.5.11. The PPPoE connection</a>
</span>
</dt>
<dt>
<span class="section">
<a href="ch05.en.html#_the_network_configuration_state_of_ifupdown">5.5.12. The network configuration state of ifupdown</a>
</span>
</dt>
<dt>
<span class="section">
<a href="ch05.en.html#_the_basic_network_reconfiguration">5.5.13. The basic network reconfiguration</a>
</span>
</dt>
<dt>
<span class="section">
<a href="ch05.en.html#_the_ifupdown_extra_package">5.5.14. The ifupdown-extra package</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="ch05.en.html#_the_advanced_network_configuration_with_ifupdown_legacy">5.6. The advanced network configuration with ifupdown (legacy)</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="ch05.en.html#_the_ifplugd_package">5.6.1. The ifplugd package</a>
</span>
</dt>
<dt>
<span class="section">
<a href="ch05.en.html#_the_ifmetric_package">5.6.2. The ifmetric package</a>
</span>
</dt>
<dt>
<span class="section">
<a href="ch05.en.html#_the_virtual_interface">5.6.3. The virtual interface</a>
</span>
</dt>
<dt>
<span class="section">
<a href="ch05.en.html#_the_advanced_command_syntax">5.6.4. The advanced command syntax</a>
</span>
</dt>
<dt>
<span class="section">
<a href="ch05.en.html#_the_mapping_stanza">5.6.5. The mapping stanza</a>
</span>
</dt>
<dt>
<span class="section">
<a href="ch05.en.html#_the_manually_switchable_network_configuration">5.6.6. The manually switchable network configuration</a>
</span>
</dt>
<dt>
<span class="section">
<a href="ch05.en.html#_scripting_with_the_ifupdown_system">5.6.7. Scripting with the ifupdown system</a>
</span>
</dt>
<dt>
<span class="section">
<a href="ch05.en.html#_mapping_with_guessnet">5.6.8. Mapping with guessnet</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="ch05.en.html#_the_low_level_network_configuration">5.7. The low level network configuration</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="ch05.en.html#_iproute2_commands">5.7.1. Iproute2 commands</a>
</span>
</dt>
<dt>
<span class="section">
<a href="ch05.en.html#_safe_low_level_network_operations">5.7.2. Safe low level network operations</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="ch05.en.html#_network_optimization">5.8. Network optimization</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="ch05.en.html#_finding_optimal_mtu">5.8.1. Finding optimal MTU</a>
</span>
</dt>
<dt>
<span class="section">
<a href="ch05.en.html#_setting_mtu">5.8.2. Setting MTU</a>
</span>
</dt>
<dt>
<span class="section">
<a href="ch05.en.html#_wan_tcp_optimization">5.8.3. WAN TCP optimization</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="ch05.en.html#_netfilter_infrastructure">5.9. Netfilter infrastructure</a>
</span>
</dt>
</dl>
</div>
<div class="tip" style="margin-left: 0.5in; margin-right: 0.5in;">
<table border="0" summary="Tip">
<tr>
<td rowspan="2" align="center" valign="top">
<img alt="[Tip]" src="images/tip.png"/>
</td>
<th align="left">Tip</th>
</tr>
<tr>
<td align="left" valign="top">
<p>For general guide to the GNU/Linux networking, read the <a class="ulink" href="http://www.tldp.org/LDP/nag2/">Linux Network Administrators Guide</a>.</p>
</td>
</tr>
</table>
</div>
<div class="tip" style="margin-left: 0.5in; margin-right: 0.5in;">
<table border="0" summary="Tip">
<tr>
<td rowspan="2" align="center" valign="top">
<img alt="[Tip]" src="images/tip.png"/>
</td>
<th align="left">Tip</th>
</tr>
<tr>
<td align="left" valign="top">
<p>For modern Debian specific guide to the networking, read <a class="ulink" href="https://www.debian.org/doc/manuals/debian-handbook/sect.network-config">The Debian Administrator's Handbook — Configuring the Network</a>.</p>
</td>
</tr>
</table>
</div>
<div class="warning" style="margin-left: 0.5in; margin-right: 0.5in;">
<table border="0" summary="Warning">
<tr>
<td rowspan="2" align="center" valign="top">
<img alt="[Warning]" src="images/warning.png"/>
</td>
<th align="left">Warning</th>
</tr>
<tr>
<td align="left" valign="top">
<p>Instead of using the traditional interface naming scheme ("<code class="literal">eth0</code>", "<code class="literal">eth1</code>", "<code class="literal">wlan0</code>", …), the newer <a class="ulink" href="http://en.wikipedia.org/wiki/Systemd">systemd</a> uses "<a class="ulink" href="https://www.freedesktop.org/wiki/Software/systemd/PredictableNetworkInterfaceNames/">Predictable Network Interface Names</a>" such as "<code class="literal">enp0s25</code>".</p>
</td>
</tr>
</table>
</div>
<div class="warning" style="margin-left: 0.5in; margin-right: 0.5in;">
<table border="0" summary="Warning">
<tr>
<td rowspan="2" align="center" valign="top">
<img alt="[Warning]" src="images/warning.png"/>
</td>
<th align="left">Warning</th>
</tr>
<tr>
<td align="left" valign="top">
<p>This chapter is getting outdated since this is based on Debian 7.0 (<code class="literal">Wheezy</code>) released in 2013.</p>
</td>
</tr>
</table>
</div>
<div class="tip" style="margin-left: 0.5in; margin-right: 0.5in;">
<table border="0" summary="Tip">
<tr>
<td rowspan="2" align="center" valign="top">
<img alt="[Tip]" src="images/tip.png"/>
</td>
<th align="left">Tip</th>
</tr>
<tr>
<td align="left" valign="top">
<p>Although this document still uses old <span class="citerefentry"><span class="refentrytitle">ifconfig</span>(8)</span> with IPv4 for its network configuration examples, Debian is moving to <span class="citerefentry"><span class="refentrytitle">ip</span>(8)</span> with IPv4+IPv6 in the <code class="literal">wheezy</code> release. Patches to update this document are welcomed.</p>
</td>
</tr>
</table>
</div>
<div class="tip" style="margin-left: 0.5in; margin-right: 0.5in;">
<table border="0" summary="Tip">
<tr>
<td rowspan="2" align="center" valign="top">
<img alt="[Tip]" src="images/tip.png"/>
</td>
<th align="left">Tip</th>
</tr>
<tr>
<td align="left" valign="top">
<p>Under <a class="ulink" href="http://en.wikipedia.org/wiki/Systemd">systemd</a>, <a class="ulink" href="http://en.wikipedia.org/wiki/Systemd#networkd">networkd</a> may be used to manage networks. See <span class="citerefentry"><span class="refentrytitle">systemd-networkd</span>(8)</span>.</p>
</td>
</tr>
</table>
</div>
<div class="section">
<div class="titlepage">
<div>
<div>
<h2 class="title"><a id="_the_basic_network_infrastructure"/>5.1. The basic network infrastructure</h2>
</div>
</div>
</div>
<p>Let's review the basic network infrastructure on the modern Debian system.</p>
<div class="table">
<a id="listofnetworkconfigurationtools"/>
<p class="title">
<strong>Table 5.1. List of network configuration tools</strong>
</p>
<div class="table-contents">
<table class="table" summary="List of network configuration tools" border="1">
<colgroup>
<col style="text-align: left"/>
<col style="text-align: left"/>
<col style="text-align: left"/>
<col style="text-align: left"/>
<col style="text-align: left"/>
</colgroup>
<thead>
<tr>
<th style="text-align: left">
packages
</th>
<th style="text-align: left">
popcon
</th>
<th style="text-align: left">
size
</th>
<th style="text-align: left">
type
</th>
<th style="text-align: left">
description
</th>
</tr>
</thead>
<tbody>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/ifupdown">
<code class="literal">ifupdown</code>
</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=ifupdown">V:561, I:995</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/i/ifupdown.html">195</a>
</td>
<td style="text-align: left">
config::ifupdown
</td>
<td style="text-align: left">
standardized tool to bring up and down the network (Debian specific)
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/ifplugd">
<code class="literal">ifplugd</code>
</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=ifplugd">V:4, I:20</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/i/ifplugd.html">214</a>
</td>
<td style="text-align: left">
, ,
</td>
<td style="text-align: left">
manage the wired network automatically
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/ifupdown-extra">
<code class="literal">ifupdown-extra</code>
</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=ifupdown-extra">V:0, I:1</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/i/ifupdown-extra.html">96</a>
</td>
<td style="text-align: left">
, ,
</td>
<td style="text-align: left">
network testing script to enhance "<code class="literal">ifupdown</code>" package
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/ifmetric">
<code class="literal">ifmetric</code>
</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=ifmetric">V:0, I:1</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/i/ifmetric.html">36</a>
</td>
<td style="text-align: left">
, ,
</td>
<td style="text-align: left">
set routing metrics for a network interface
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/guessnet">
<code class="literal">guessnet</code>
</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=guessnet">V:0, I:0</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/g/guessnet.html">422</a>
</td>
<td style="text-align: left">
, ,
</td>
<td style="text-align: left">
mapping script to enhance "<code class="literal">ifupdown</code>" package via "<code class="literal">/etc/network/interfaces</code>" file
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/ifscheme">
<code class="literal">ifscheme</code>
</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=ifscheme">V:0, I:0</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/i/ifscheme.html">58</a>
</td>
<td style="text-align: left">
, ,
</td>
<td style="text-align: left">
mapping scripts to enhance "<code class="literal">ifupdown</code>" package
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/ifupdown-scripts-zg2">
<code class="literal">ifupdown-scripts-zg2</code>
</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=ifupdown-scripts-zg2">V:0, I:0</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/i/ifupdown-scripts-zg2.html">147</a>
</td>
<td style="text-align: left">
, ,
</td>
<td style="text-align: left">
Zugschlus' interface scripts for ifupdown's manual method
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/network-manager">
<code class="literal">network-manager</code>
</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=network-manager">V:366, I:469</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/n/network-manager.html">10172</a>
</td>
<td style="text-align: left">
config::NM
</td>
<td style="text-align: left"><a class="ulink" href="http://en.wikipedia.org/wiki/NetworkManager">NetworkManager</a> (daemon): manage the network automatically
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/network-manager-gnome">
<code class="literal">network-manager-gnome</code>
</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=network-manager-gnome">V:236, I:411</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/n/network-manager-gnome.html">6281</a>
</td>
<td style="text-align: left">
, ,
</td>
<td style="text-align: left"><a class="ulink" href="http://en.wikipedia.org/wiki/NetworkManager">NetworkManager</a> (GNOME frontend)
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/wicd">
<code class="literal">wicd</code>
</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=wicd">I:35</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/w/wicd.html">35</a>
</td>
<td style="text-align: left">
config::wicd
</td>
<td style="text-align: left">
wired and wireless network manager (metapackage)
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/wicd-cli">
<code class="literal">wicd-cli</code>
</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=wicd-cli">V:0, I:2</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/w/wicd-cli.html">59</a>
</td>
<td style="text-align: left">
, ,
</td>
<td style="text-align: left">
wired and wireless network manager (command-line client)
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/wicd-curses">
<code class="literal">wicd-curses</code>
</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=wicd-curses">V:1, I:5</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/w/wicd-curses.html">175</a>
</td>
<td style="text-align: left">
, ,
</td>
<td style="text-align: left">
wired and wireless network manager (Curses client)
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/wicd-daemon">
<code class="literal">wicd-daemon</code>
</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=wicd-daemon">V:30, I:40</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/w/wicd-daemon.html">954</a>
</td>
<td style="text-align: left">
, ,
</td>
<td style="text-align: left">
wired and wireless network manager (daemon)
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/wicd-gtk">
<code class="literal">wicd-gtk</code>
</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=wicd-gtk">V:24, I:37</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/w/wicd-gtk.html">574</a>
</td>
<td style="text-align: left">
, ,
</td>
<td style="text-align: left">
wired and wireless network manager (GTK+ client)
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/iptables">
<code class="literal">iptables</code>
</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=iptables">V:240, I:993</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/i/iptables.html">1528</a>
</td>
<td style="text-align: left">
config::Netfilter
</td>
<td style="text-align: left">
administration tools for packet filtering and NAT (<a class="ulink" href="http://en.wikipedia.org/wiki/Netfilter">Netfilter</a>)
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/iproute">
<code class="literal">iproute</code>
</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=iproute">V:107, I:475</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/i/iproute.html">23</a>
</td>
<td style="text-align: left">
config::iproute2
</td>
<td style="text-align: left"><a class="ulink" href="http://www.linuxfoundation.org/collaborate/workgroups/networking/iproute2">iproute2</a>, IPv6 and other advanced network configuration: <span class="citerefentry"><span class="refentrytitle">ip</span>(8)</span>, <span class="citerefentry"><span class="refentrytitle">tc</span>(8)</span>, etc
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/ifrename">
<code class="literal">ifrename</code>
</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=ifrename">V:0, I:2</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/i/ifrename.html">122</a>
</td>
<td style="text-align: left">
, ,
</td>
<td style="text-align: left">
rename network interfaces based on various static criteria: <span class="citerefentry"><span class="refentrytitle">ifrename</span>(8)</span>
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/ethtool">
<code class="literal">ethtool</code>
</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=ethtool">V:94, I:266</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/e/ethtool.html">372</a>
</td>
<td style="text-align: left">
, ,
</td>
<td style="text-align: left">
display or change Ethernet device settings
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/iputils-ping">
<code class="literal">iputils-ping</code>
</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=iputils-ping">V:257, I:997</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/i/iputils-ping.html">111</a>
</td>
<td style="text-align: left">
test::iproute2
</td>
<td style="text-align: left">
test network reachability of a remote host by <a class="ulink" href="http://en.wikipedia.org/wiki/Hostname">hostname</a> or <a class="ulink" href="http://en.wikipedia.org/wiki/IP_address">IP address</a> (<a class="ulink" href="http://www.linuxfoundation.org/collaborate/workgroups/networking/iproute2">iproute2</a>)
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/iputils-arping">
<code class="literal">iputils-arping</code>
</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=iputils-arping">V:66, I:405</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/i/iputils-arping.html">58</a>
</td>
<td style="text-align: left">
, ,
</td>
<td style="text-align: left">
test network reachability of a remote host specified by the <a class="ulink" href="http://en.wikipedia.org/wiki/Address_Resolution_Protocol">ARP</a> address
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/iputils-tracepath">
<code class="literal">iputils-tracepath</code>
</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=iputils-tracepath">V:14, I:264</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/i/iputils-tracepath.html">75</a>
</td>
<td style="text-align: left">
, ,
</td>
<td style="text-align: left">
trace the network path to a remote host
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/net-tools">
<code class="literal">net-tools</code>
</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=net-tools">V:395, I:976</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/n/net-tools.html">940</a>
</td>
<td style="text-align: left">
config::net-tools
</td>
<td style="text-align: left">
NET-3 networking toolkit (<a class="ulink" href="http://www.linuxfoundation.org/collaborate/workgroups/networking/net-tools">net-tools</a>, IPv4 network configuration): <span class="citerefentry"><span class="refentrytitle">ifconfig</span>(8)</span> etc.
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/inetutils-ping">
<code class="literal">inetutils-ping</code>
</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=inetutils-ping">V:0, I:1</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/i/inetutils-ping.html">337</a>
</td>
<td style="text-align: left">
test::net-tools
</td>
<td style="text-align: left">
test network reachability of a remote host by <a class="ulink" href="http://en.wikipedia.org/wiki/Hostname">hostname</a> or <a class="ulink" href="http://en.wikipedia.org/wiki/IP_address">IP address</a> (legacy, GNU)
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/arping">
<code class="literal">arping</code>
</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=arping">V:1, I:28</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/a/arping.html">67</a>
</td>
<td style="text-align: left">
, ,
</td>
<td style="text-align: left">
test network reachability of a remote host specified by the <a class="ulink" href="http://en.wikipedia.org/wiki/Address_Resolution_Protocol">ARP</a> address (legacy)
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/traceroute">
<code class="literal">traceroute</code>
</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=traceroute">V:68, I:992</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/t/traceroute.html">154</a>
</td>
<td style="text-align: left">
, ,
</td>
<td style="text-align: left">
trace the network path to a remote host (legacy, console)
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/isc-dhcp-client">
<code class="literal">isc-dhcp-client</code>
</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=isc-dhcp-client">V:406, I:963</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/i/isc-dhcp-client.html">649</a>
</td>
<td style="text-align: left">
config::low-level
</td>
<td style="text-align: left">
DHCP client
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/wpasupplicant">
<code class="literal">wpasupplicant</code>
</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=wpasupplicant">V:294, I:544</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/w/wpasupplicant.html">2528</a>
</td>
<td style="text-align: left">
, ,
</td>
<td style="text-align: left">
client support for WPA and WPA2 (IEEE 802.11i)
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/wpagui">
<code class="literal">wpagui</code>
</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=wpagui">V:0, I:3</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/w/wpagui.html">780</a>
</td>
<td style="text-align: left">
, ,
</td>
<td style="text-align: left">
Qt GUI client for wpa_supplicant
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/wireless-tools">
<code class="literal">wireless-tools</code>
</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=wireless-tools">V:94, I:274</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/w/wireless-tools.html">286</a>
</td>
<td style="text-align: left">
, ,
</td>
<td style="text-align: left">
tools for manipulating Linux Wireless Extensions
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/ppp">
<code class="literal">ppp</code>
</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=ppp">V:186, I:515</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/p/ppp.html">927</a>
</td>
<td style="text-align: left">
, ,
</td>
<td style="text-align: left">
PPP/PPPoE connection with <code class="literal">chat</code>
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/pppoeconf">
<code class="literal">pppoeconf</code>
</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=pppoeconf">V:0, I:11</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/p/pppoeconf.html">290</a>
</td>
<td style="text-align: left">
config::helper
</td>
<td style="text-align: left">
configuration helper for PPPoE connection
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/pppconfig">
<code class="literal">pppconfig</code>
</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=pppconfig">V:1, I:3</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/p/pppconfig.html">805</a>
</td>
<td style="text-align: left">
, ,
</td>
<td style="text-align: left">
configuration helper for PPP connection with <code class="literal">chat</code>
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/wvdial">
<code class="literal">wvdial</code>
</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=wvdial">V:0, I:7</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/w/wvdial.html">276</a>
</td>
<td style="text-align: left">
, ,
</td>
<td style="text-align: left">
configuration helper for PPP connection with <code class="literal">wvdial</code> and <code class="literal">ppp</code>
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/mtr-tiny">
<code class="literal">mtr-tiny</code>
</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=mtr-tiny">V:7, I:58</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/m/mtr-tiny.html">138</a>
</td>
<td style="text-align: left">
test::low-level
</td>
<td style="text-align: left">
trace the network path to a remote host (curses)
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/mtr">
<code class="literal">mtr</code>
</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=mtr">V:5, I:40</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/m/mtr.html">190</a>
</td>
<td style="text-align: left">
, ,
</td>
<td style="text-align: left">
trace the network path to a remote host (curses and GTK+)
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/gnome-nettool">
<code class="literal">gnome-nettool</code>
</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=gnome-nettool">V:11, I:257</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/g/gnome-nettool.html">2116</a>
</td>
<td style="text-align: left">
, ,
</td>
<td style="text-align: left">
tools for common network information operations (GNOME)
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/nmap">
<code class="literal">nmap</code>
</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=nmap">V:45, I:432</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/n/nmap.html">22707</a>
</td>
<td style="text-align: left">
, ,
</td>
<td style="text-align: left">
network mapper / port scanner (<a class="ulink" href="http://en.wikipedia.org/wiki/Nmap">Nmap</a>, console)
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/zenmap">
<code class="literal">zenmap</code>
</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=zenmap">V:3, I:12</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/z/zenmap.html">2842</a>
</td>
<td style="text-align: left">
, ,
</td>
<td style="text-align: left">
network mapper / port scanner (GTK+)
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/tcpdump">
<code class="literal">tcpdump</code>
</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=tcpdump">V:20, I:199</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/t/tcpdump.html">1175</a>
</td>
<td style="text-align: left">
, ,
</td>
<td style="text-align: left">
network traffic analyzer (<a class="ulink" href="http://en.wikipedia.org/wiki/Tcpdump">Tcpdump</a>, console)
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/wireshark">
<code class="literal">wireshark</code>
</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=wireshark">V:5, I:64</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/w/wireshark.html">71</a>
</td>
<td style="text-align: left">
, ,
</td>
<td style="text-align: left">
network traffic analyzer (<a class="ulink" href="http://en.wikipedia.org/wiki/Wireshark">Wireshark</a>, GTK+)
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/tshark">
<code class="literal">tshark</code>
</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=tshark">V:3, I:38</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/t/tshark.html">370</a>
</td>
<td style="text-align: left">
, ,
</td>
<td style="text-align: left">
network traffic analyzer (console)
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/nagios3">
<code class="literal">nagios3</code>
</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=nagios3">I:8</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/n/nagios3.html">NOT_FOUND</a>
</td>
<td style="text-align: left">
, ,
</td>
<td style="text-align: left">
monitoring and management system for hosts, services and networks (<a class="ulink" href="http://en.wikipedia.org/wiki/Nagios">Nagios</a>)
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/tcptrace">
<code class="literal">tcptrace</code>
</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=tcptrace">V:0, I:1</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/t/tcptrace.html">392</a>
</td>
<td style="text-align: left">
, ,
</td>
<td style="text-align: left">
produce a summarization of the connections from <code class="literal">tcpdump</code> output
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/snort">
<code class="literal">snort</code>
</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=snort">V:0, I:1</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/s/snort.html">1920</a>
</td>
<td style="text-align: left">
, ,
</td>
<td style="text-align: left">
flexible network intrusion detection system (<a class="ulink" href="http://en.wikipedia.org/wiki/Snort_(software)">Snort</a>)
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/ntopng">
<code class="literal">ntopng</code>
</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=ntopng">V:0, I:1</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/n/ntopng.html">684</a>
</td>
<td style="text-align: left">
, ,
</td>
<td style="text-align: left">
display network usage in web browser
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/dnsutils">
<code class="literal">dnsutils</code>
</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=dnsutils">V:80, I:876</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/d/dnsutils.html">518</a>
</td>
<td style="text-align: left">
, ,
</td>
<td style="text-align: left">
network clients provided with <a class="ulink" href="http://en.wikipedia.org/wiki/BIND">BIND</a>: <span class="citerefentry"><span class="refentrytitle">nslookup</span>(8)</span>, <span class="citerefentry"><span class="refentrytitle">nsupdate</span>(8)</span>, <span class="citerefentry"><span class="refentrytitle">dig</span>(8)</span>
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/dlint">
<code class="literal">dlint</code>
</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=dlint">V:0, I:19</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/d/dlint.html">96</a>
</td>
<td style="text-align: left">
, ,
</td>
<td style="text-align: left">
check <a class="ulink" href="http://en.wikipedia.org/wiki/Domain_Name_System">DNS</a> zone information using nameserver lookups
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/dnstracer">
<code class="literal">dnstracer</code>
</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=dnstracer">V:0, I:2</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/d/dnstracer.html">56</a>
</td>
<td style="text-align: left">
, ,
</td>
<td style="text-align: left">
trace a chain of <a class="ulink" href="http://en.wikipedia.org/wiki/Domain_Name_System">DNS</a> servers to the source
</td>
</tr>
</tbody>
</table>
</div>
</div>
<br class="table-break"/>
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="_the_hostname_resolution"/>5.1.1. The hostname resolution</h3>
</div>
</div>
</div>
<p>The hostname resolution is currently supported by the <a class="ulink" href="http://en.wikipedia.org/wiki/Name_Service_Switch">NSS (Name Service Switch)</a> mechanism too. The flow of this resolution is the following.</p>
<div class="orderedlist">
<ol class="orderedlist">
<li class="listitem">
<p>
The "<code class="literal">/etc/nsswitch.conf</code>" file with stanza like "<code class="literal">hosts: files dns</code>" dictates the hostname resolution order. (This replaces the old functionality of the "<code class="literal">order</code>" stanza in "<code class="literal">/etc/host.conf</code>".)
</p>
</li>
<li class="listitem">
<p>
The <code class="literal">files</code> method is invoked first. If the hostname is found in the "<code class="literal">/etc/hosts</code>" file, it returns all valid addresses for it and exits. (The "<code class="literal">/etc/host.conf</code>" file contains "<code class="literal">multi on</code>".)
</p>
</li>
<li class="listitem">
<p>
The <code class="literal">dns</code> method is invoked. If the hostname is found by the query to the <a class="ulink" href="http://en.wikipedia.org/wiki/Domain_Name_System">Internet Domain Name System (DNS)</a> identified by the "<code class="literal">/etc/resolv.conf</code>" file, it returns all valid addresses for it and exits.
</p>
</li>
</ol>
</div>
<p>For example, "<code class="literal">/etc/hosts</code>" looks like the following.</p>
<pre class="screen">127.0.0.1 localhost
127.0.1.1 <host_name>
# The following lines are desirable for IPv6 capable hosts
::1 ip6-localhost ip6-loopback
fe00::0 ip6-localnet
ff00::0 ip6-mcastprefix
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters
ff02::3 ip6-allhosts</pre>
<p>Each line starts with a <a class="ulink" href="http://en.wikipedia.org/wiki/IP_address">IP address</a> and it is followed by the associated <a class="ulink" href="http://en.wikipedia.org/wiki/Hostname">hostname</a>.</p>
<p>The IP address <code class="literal">127.0.1.1</code> in the second line of this example may not be found on some other Unix-like systems. The <a class="ulink" href="http://en.wikipedia.org/wiki/Debian-Installer">Debian Installer</a> creates this entry for a system without a permanent IP address as a workaround for some software (e.g., GNOME) as documented in the <a class="ulink" href="http://bugs.debian.org/719621">bug #719621</a>.</p>
<p>The <host_name> matches the hostname defined in the "<code class="literal">/etc/hostname</code>".</p>
<p>For a system with a permanent IP address, that permanent IP address should be used here instead of <code class="literal">127.0.1.1</code>.</p>
<p>For a system with a permanent IP address and a <a class="ulink" href="http://en.wikipedia.org/wiki/FQDN">fully qualified domain name (FQDN)</a> provided by the <a class="ulink" href="http://en.wikipedia.org/wiki/Domain_Name_System">Domain Name System (DNS)</a>, that canonical <host_name>.<domain_name> should be used instead of just <host_name>.</p>
<p>The "<code class="literal">/etc/resolv.conf</code>" is a static file if the <code class="literal">resolvconf</code> package is not installed. If installed, it is a symbolic link. Either way, it contains information that initialize the resolver routines. If the DNS is found at IP="<code class="literal">192.168.11.1</code>", it contains the following.</p>
<pre class="screen">nameserver 192.168.11.1</pre>
<p>The <code class="literal">resolvconf</code> package makes this "<code class="literal">/etc/resolv.conf</code>" into a symbolic link and manages its contents by the hook scripts automatically.</p>
<p>For the PC workstation on the typical adhoc LAN environment, the hostname can be resolved via Multicast DNS (mDNS, <a class="ulink" href="http://en.wikipedia.org/wiki/Zeroconf">Zeroconf</a>) in addition to the basic <code class="literal">files</code> and <code class="literal">dns</code> methods.</p>
<div class="itemizedlist">
<ul class="itemizedlist">
<li class="listitem">
<p><a class="ulink" href="http://en.wikipedia.org/wiki/Avahi_(software)">Avahi</a> provides a framework for Multicast DNS Service Discovery on Debian.
</p>
</li>
<li class="listitem">
<p>
It is equivalent of <a class="ulink" href="http://en.wikipedia.org/wiki/Bonjour_(software)">Apple Bonjour / Apple Rendezvous</a>.
</p>
</li>
<li class="listitem">
<p>
The <code class="literal">libnss-mdns</code> plugin package provides host name resolution via mDNS for the GNU Name Service Switch (NSS) functionality of the GNU C Library (glibc).
</p>
</li>
<li class="listitem">
<p>
The "<code class="literal">/etc/nsswitch.conf</code>" file should have stanza like "<code class="literal">hosts: files mdns4_minimal [NOTFOUND=return] dns mdns4</code>".
</p>
</li>
<li class="listitem">
<p>
Host names ending with the <a class="ulink" href="http://en.wikipedia.org/wiki/.local">".local"</a> <a class="ulink" href="http://en.wikipedia.org/wiki/Pseudo-top-level_domain">pseudo-top-level domain</a> (TLD) are resolved.
</p>
</li>
<li class="listitem">
<p>
The mDNS IPv4 link-local multicast address "<code class="literal">224.0.0.251</code>" or its IPv6 equivalent "<code class="literal">FF02::FB</code>" are used to make DNS query for a name ending with "<code class="literal">.local</code>".
</p>
</li>
</ul>
</div>
<p>The hostname resolution via deprecated <a class="ulink" href="http://en.wikipedia.org/wiki/NetBIOS_over_TCP/IP">NETBios over TCP/IP</a> used by the older Windows system can be provided by installing the <code class="literal">winbind</code> package. The "<code class="literal">/etc/nsswitch.conf</code>" file should have stanza like "<code class="literal">hosts: files mdns4_minimal [NOTFOUND=return] dns mdns4 wins</code>" to enable this functionality. (Modern Windows system usually use the <code class="literal">dns</code> method for the hostname resolution.)</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<table border="0" summary="Note">
<tr>
<td rowspan="2" align="center" valign="top">
<img alt="[Note]" src="images/note.png"/>
</td>
<th align="left">Note</th>
</tr>
<tr>
<td align="left" valign="top">
<p>The <a class="ulink" href="http://newgtlds.icann.org/en/program-status/delegated-strings">expansion of generic Top-Level Domains (gTLD)</a> in the <a class="ulink" href="http://en.wikipedia.org/wiki/Domain_Name_System">Domain Name System</a> is underway. Watch out for the <a class="ulink" href="http://icannwiki.com/Name_Collision">name collision</a> when chosing a domain name used only within LAN.</p>
</td>
</tr>
</table>
</div>
</div>
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="_the_network_interface_name"/>5.1.2. The network interface name</h3>
</div>
</div>
</div>
<p>The network interface name, e.g. <code class="literal">eth0</code>, is assigned to each hardware in the Linux kernel through the user space configuration mechanism, <code class="literal">udev</code> (see <a class="xref" href="ch03.en.html#_the_udev_system" title="3.3. The udev system">Section 3.3, “The udev system”</a>), as it is found. The network interface name is referred as <span class="strong"><strong>physical interface</strong></span> in <span class="citerefentry"><span class="refentrytitle">ifup</span>(8)</span> and <span class="citerefentry"><span class="refentrytitle">interfaces</span>(5)</span>.</p>
<p>In order to ensure each network interface to be named persistently for each reboot using <a class="ulink" href="http://en.wikipedia.org/wiki/MAC_address">MAC address</a> etc., there is a rules file "<code class="literal">/etc/udev/rules.d/70-persistent-net.rules</code>". This file is automatically generated by the "<code class="literal">/lib/udev/write_net_rules</code>" program, probably run by the "<code class="literal">persistent-net-generator.rules</code>" rules file. You can modify it to change naming rule.</p>
<div class="caution" style="margin-left: 0.5in; margin-right: 0.5in;">
<table border="0" summary="Caution">
<tr>
<td rowspan="2" align="center" valign="top">
<img alt="[Caution]" src="images/caution.png"/>
</td>
<th align="left">Caution</th>
</tr>
<tr>
<td align="left" valign="top">
<p>When editing the "<code class="literal">/etc/udev/rules.d/70-persistent-net.rules</code>" rules file, you must keep each rule on a single line and the <a class="ulink" href="http://en.wikipedia.org/wiki/MAC_address">MAC address</a> in lowercase. For example, if you find "FireWire device" and "PCI device" in this file, you probably want to name "PCI device" as <code class="literal">eth0</code> and configure it as the primary network interface.</p>
</td>
</tr>
</table>
</div>
</div>
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="_the_network_address_range_for_the_lan"/>5.1.3. The network address range for the LAN</h3>
</div>
</div>
</div>
<p>Let us be reminded of the IPv4 32 bit address ranges in each class reserved for use on the <a class="ulink" href="http://en.wikipedia.org/wiki/Local_area_network">local area networks (LANs)</a> by <a class="ulink" href="http://tools.ietf.org/html/rfc1918">rfc1918</a>. These addresses are guaranteed not to conflict with any addresses on the Internet proper.</p>
<div class="table">
<a id="listofnetworkaddressranges"/>
<p class="title">
<strong>Table 5.2. List of network address ranges</strong>
</p>
<div class="table-contents">
<table class="table" summary="List of network address ranges" border="1">
<colgroup>
<col style="text-align: left"/>
<col style="text-align: left"/>
<col style="text-align: left"/>
<col style="text-align: left"/>
<col style="text-align: left"/>
</colgroup>
<thead>
<tr>
<th style="text-align: left">
Class
</th>
<th style="text-align: left">
network addresses
</th>
<th style="text-align: left">
net mask
</th>
<th style="text-align: left">
net mask /bits
</th>
<th style="text-align: left">
# of subnets
</th>
</tr>
</thead>
<tbody>
<tr>
<td style="text-align: left">
A
</td>
<td style="text-align: left">
10.x.x.x
</td>
<td style="text-align: left">
255.0.0.0
</td>
<td style="text-align: left">
/8
</td>
<td style="text-align: left">
1
</td>
</tr>
<tr>
<td style="text-align: left">
B
</td>
<td style="text-align: left">
172.16.x.x — 172.31.x.x
</td>
<td style="text-align: left">
255.255.0.0
</td>
<td style="text-align: left">
/16
</td>
<td style="text-align: left">
16
</td>
</tr>
<tr>
<td style="text-align: left">
C
</td>
<td style="text-align: left">
192.168.0.x — 192.168.255.x
</td>
<td style="text-align: left">
255.255.255.0
</td>
<td style="text-align: left">
/24
</td>
<td style="text-align: left">
256
</td>
</tr>
</tbody>
</table>
</div>
</div>
<br class="table-break"/>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<table border="0" summary="Note">
<tr>
<td rowspan="2" align="center" valign="top">
<img alt="[Note]" src="images/note.png"/>
</td>
<th align="left">Note</th>
</tr>
<tr>
<td align="left" valign="top">
<p>If one of these addresses is assigned to a host, then that host must not access the Internet directly but must access it through a gateway that acts as a proxy for individual services or else does <a class="ulink" href="http://en.wikipedia.org/wiki/Network_address_translation">Network Address Translation (NAT)</a>. The broadband router usually performs NAT for the consumer LAN environment.</p>
</td>
</tr>
</table>
</div>
</div>
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="_the_network_device_support"/>5.1.4. The network device support</h3>
</div>
</div>
</div>
<p>Although most hardware devices are supported by the Debian system, there are some network devices which require <a class="ulink" href="http://www.debian.org/social_contract#guidelines">DFSG</a> non-free firmware to support them. Please see <a class="xref" href="ch09.en.html#_hardware_drivers_and_firmware" title="9.9.6. Hardware drivers and firmware">Section 9.9.6, “Hardware drivers and firmware”</a>.</p>
</div>
</div>
<div class="section">
<div class="titlepage">
<div>
<div>
<h2 class="title"><a id="_the_modern_network_configuration_for_desktop"/>5.2. The modern network configuration for desktop</h2>
</div>
</div>
</div>
<p>Debian <code class="literal">squeeze</code> and newer can manage the network connection via management <a class="ulink" href="http://en.wikipedia.org/wiki/Daemon_(computer_software)">daemon</a> software such as <a class="ulink" href="http://en.wikipedia.org/wiki/NetworkManager">NetworkManager (NM)</a> (network-manager and associated packages) or <a class="ulink" href="http://en.wikipedia.org/wiki/Wicd_(Linux_Network_Manager)">Wicd</a> (wicd and associated packages).</p>
<div class="itemizedlist">
<ul class="itemizedlist">
<li class="listitem">
<p>
They come with their own <a class="ulink" href="http://en.wikipedia.org/wiki/Graphical_user_interface">GUI</a> and command-line programs as their user interfaces.
</p>
</li>
<li class="listitem">
<p>
They come with their own <a class="ulink" href="http://en.wikipedia.org/wiki/Daemon_(computer_software)">daemon</a> as their backend system.
</p>
</li>
<li class="listitem">
<p>
They allow easy connection of your system to the Internet.
</p>
</li>
<li class="listitem">
<p>
They allow easy management of wired and wireless network configuration.
</p>
</li>
<li class="listitem">
<p>
They allow us to configure network independent of the legacy <code class="literal">ifupdown</code> package.
</p>
</li>
</ul>
</div>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<table border="0" summary="Note">
<tr>
<td rowspan="2" align="center" valign="top">
<img alt="[Note]" src="images/note.png"/>
</td>
<th align="left">Note</th>
</tr>
<tr>
<td align="left" valign="top">
<p>Do not use these automatic network configuration tools for servers. These are aimed primarily for mobile desktop users on laptops.</p>
</td>
</tr>
</table>
</div>
<p>These modern network configuration tools need to be configured properly to avoid conflicting with the legacy <code class="literal">ifupdown</code> package and its configuration file "<code class="literal">/etc/network/interfaces</code>".</p>
<div class="tip" style="margin-left: 0.5in; margin-right: 0.5in;">
<table border="0" summary="Tip">
<tr>
<td rowspan="2" align="center" valign="top">
<img alt="[Tip]" src="images/tip.png"/>
</td>
<th align="left">Tip</th>
</tr>
<tr>
<td align="left" valign="top">
<p>Under <a class="ulink" href="http://en.wikipedia.org/wiki/Systemd">systemd</a>, the network may be configured in <code class="literal">/etc/systemd/network/</code> instead. See <span class="citerefentry"><span class="refentrytitle">systemd-resolved</span>(8)</span>, <span class="citerefentry"><span class="refentrytitle">resolved.conf</span>(5)</span>, and <span class="citerefentry"><span class="refentrytitle">systemd-networkd</span>(8)</span>.</p>
</td>
</tr>
</table>
</div>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<table border="0" summary="Note">
<tr>
<td rowspan="2" align="center" valign="top">
<img alt="[Note]" src="images/note.png"/>
</td>
<th align="left">Note</th>
</tr>
<tr>
<td align="left" valign="top">
<p>Some features of these automatic network configuration tools may suffer regressions. These are not as robust as the legacy <code class="literal">ifupdown</code> package. Check <a class="ulink" href="http://bugs.debian.org/cgi-bin/pkgreport.cgi?package=network-manager">BTS of network-manager</a> and <a class="ulink" href="http://bugs.debian.org/cgi-bin/pkgreport.cgi?package=wicd">BTS of wicd</a> for current issues and limitations.</p>
</td>
</tr>
</table>
</div>
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="_gui_network_configuration_tools"/>5.2.1. GUI network configuration tools</h3>
</div>
</div>
</div>
<p>Official documentations for NM and Wicd on Debian are provided in "<code class="literal">/usr/share/doc/network-manager/README.Debian</code>" and "<code class="literal">/usr/share/doc/wicd/README.Debian</code>", respectively.</p>
<p>Essentially, the network configuration for desktop is done as follows.</p>
<div class="orderedlist">
<ol class="orderedlist">
<li class="listitem">
<p>
Make desktop user, e.g. <code class="literal">foo</code>, belong to group "<code class="literal">netdev</code>" by the following (Alternatively, do it automatically via <a class="ulink" href="http://en.wikipedia.org/wiki/D-Bus">D-bus</a> under modern desktop environments such as GNOME and KDE).
</p>
<pre class="screen">$ sudo adduser foo netdev</pre>
</li>
<li class="listitem">
<p>
Keep configuration of "<code class="literal">/etc/network/interfaces</code>" as simple as in the following.
</p>
<pre class="screen">auto lo
iface lo inet loopback</pre>
</li>
<li class="listitem">
<p>
Restart NM or Wicd by the following.
</p>
<pre class="screen">$ sudo /etc/init.d/network-manager restart</pre>
<pre class="screen">$ sudo /etc/init.d/wicd restart</pre>
</li>
<li class="listitem">
<p>
Configure your network via GUI.
</p>
</li>
</ol>
</div>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<table border="0" summary="Note">
<tr>
<td rowspan="2" align="center" valign="top">
<img alt="[Note]" src="images/note.png"/>
</td>
<th align="left">Note</th>
</tr>
<tr>
<td align="left" valign="top">
<p>Only interfaces which are <span class="strong"><strong>not</strong></span> listed in "<code class="literal">/etc/network/interfaces</code>" are managed by NM or Wicd to avoid conflict with <code class="literal">ifupdown</code>.</p>
</td>
</tr>
</table>
</div>
<div class="tip" style="margin-left: 0.5in; margin-right: 0.5in;">
<table border="0" summary="Tip">
<tr>
<td rowspan="2" align="center" valign="top">
<img alt="[Tip]" src="images/tip.png"/>
</td>
<th align="left">Tip</th>
</tr>
<tr>
<td align="left" valign="top">
<p>If you wish to extend network configuration capabilities of NM, please seek appropriate plug-in modules and supplemental packages such as <code class="literal">network-manager-openconnect</code>, <code class="literal">network-manager-openvpn-gnome</code>, <code class="literal">network-manager-pptp-gnome</code>, <code class="literal">mobile-broadband-provider-info</code>, <code class="literal">gnome-bluetooth</code>, etc. The same goes for those of Wicd.</p>
</td>
</tr>
</table>
</div>
<div class="caution" style="margin-left: 0.5in; margin-right: 0.5in;">
<table border="0" summary="Caution">
<tr>
<td rowspan="2" align="center" valign="top">
<img alt="[Caution]" src="images/caution.png"/>
</td>
<th align="left">Caution</th>
</tr>
<tr>
<td align="left" valign="top">
<p>These automatic network configuration tools may not be compatible with esoteric configurations of legacy <code class="literal">ifupdown</code> in "<code class="literal">/etc/network/interfaces</code>" such as ones in <a class="xref" href="ch05.en.html#_the_basic_network_configuration_with_ifupdown_legacy" title="5.5. The basic network configuration with ifupdown (legacy)">Section 5.5, “The basic network configuration with ifupdown (legacy)”</a> and <a class="xref" href="ch05.en.html#_the_advanced_network_configuration_with_ifupdown_legacy" title="5.6. The advanced network configuration with ifupdown (legacy)">Section 5.6, “The advanced network configuration with ifupdown (legacy)”</a>. Check <a class="ulink" href="http://bugs.debian.org/cgi-bin/pkgreport.cgi?package=network-manager">BTS of network-manager</a> and <a class="ulink" href="http://bugs.debian.org/cgi-bin/pkgreport.cgi?package=wicd">BTS of wicd</a> for current issues and limitations.</p>
</td>
</tr>
</table>
</div>
</div>
</div>
<div class="section">
<div class="titlepage">
<div>
<div>
<h2 class="title"><a id="_the_legacy_network_connection_and_configuration"/>5.3. The legacy network connection and configuration</h2>
</div>
</div>
</div>
<p>When the method described in <a class="xref" href="ch05.en.html#_the_modern_network_configuration_for_desktop" title="5.2. The modern network configuration for desktop">Section 5.2, “The modern network configuration for desktop”</a> does not suffice your needs, you should use the legacy network connection and configuration method which combines many simpler tools.</p>
<p>The legacy network connection is specific for each method (see <a class="xref" href="ch05.en.html#_the_network_connection_method_legacy" title="5.4. The network connection method (legacy)">Section 5.4, “The network connection method (legacy)”</a>).</p>
<p>There are 2 types of programs for the low level network configuration on Linux (see <a class="xref" href="ch05.en.html#_iproute2_commands" title="5.7.1. Iproute2 commands">Section 5.7.1, “Iproute2 commands”</a>).</p>
<div class="itemizedlist">
<ul class="itemizedlist">
<li class="listitem">
<p>
Old <a class="ulink" href="http://www.linuxfoundation.org/collaborate/workgroups/networking/net-tools">net-tools</a> programs (<span class="citerefentry"><span class="refentrytitle">ifconfig</span>(8)</span>, …) are from the Linux NET-3 networking system. Most of these are obsolete now.
</p>
</li>
<li class="listitem">
<p>
New <a class="ulink" href="http://www.linuxfoundation.org/collaborate/workgroups/networking/iproute2">Linux iproute2</a> programs (<span class="citerefentry"><span class="refentrytitle">ip</span>(8)</span>, …) are the current Linux networking system.
</p>
</li>
</ul>
</div>
<p>Although these low level networking programs are powerful, they are cumbersome to use. So high level network configuration systems have been created.</p>
<p>The <code class="literal">ifupdown</code> package is the de facto standard for such high level network configuration system on Debian. It enables you to bring up network simply by doing , e.g., "<code class="literal">ifup eth0</code>". Its configuration file is the "<code class="literal">/etc/network/interfaces</code>" file and its typical contents are the following.</p>
<pre class="screen">auto lo
iface lo inet loopback
auto eth0
iface eth0 inet dhcp</pre>
<p>The <code class="literal">resolvconf</code> package was created to supplement <code class="literal">ifupdown</code> system to support smooth reconfiguration of network address resolution by automating rewrite of resolver configuration file "<code class="literal">/etc/resolv.conf</code>". Now, most Debian network configuration packages are modified to use <code class="literal">resolvconf</code> package (see "<code class="literal">/usr/share/doc/resolvconf/README.Debian</code>").</p>
<p>Helper scripts to the <code class="literal">ifupdown</code> package such as <code class="literal">ifplugd</code>, <code class="literal">guessnet</code>, <code class="literal">ifscheme</code>, etc. are created to automate dynamic configuration of network environment such as one for mobile PC on wired LAN. These are relatively difficult to use but play well with existing <code class="literal">ifupdown</code> system.</p>
<p>These are explained in detail with examples (see <a class="xref" href="ch05.en.html#_the_basic_network_configuration_with_ifupdown_legacy" title="5.5. The basic network configuration with ifupdown (legacy)">Section 5.5, “The basic network configuration with ifupdown (legacy)”</a> and <a class="xref" href="ch05.en.html#_the_advanced_network_configuration_with_ifupdown_legacy" title="5.6. The advanced network configuration with ifupdown (legacy)">Section 5.6, “The advanced network configuration with ifupdown (legacy)”</a>).</p>
</div>
<div class="section">
<div class="titlepage">
<div>
<div>
<h2 class="title"><a id="_the_network_connection_method_legacy"/>5.4. The network connection method (legacy)</h2>
</div>
</div>
</div>
<div class="caution" style="margin-left: 0.5in; margin-right: 0.5in;">
<table border="0" summary="Caution">
<tr>
<td rowspan="2" align="center" valign="top">
<img alt="[Caution]" src="images/caution.png"/>
</td>
<th align="left">Caution</th>
</tr>
<tr>
<td align="left" valign="top">
<p>The connection test methods described in this section are meant for testing purposes. It is not meant to be used directly for the daily network connection. You are advised to use NM, Wicd, or the <code class="literal">ifupdown</code> package instead (see <a class="xref" href="ch05.en.html#_the_modern_network_configuration_for_desktop" title="5.2. The modern network configuration for desktop">Section 5.2, “The modern network configuration for desktop”</a> and <a class="xref" href="ch05.en.html#_the_basic_network_configuration_with_ifupdown_legacy" title="5.5. The basic network configuration with ifupdown (legacy)">Section 5.5, “The basic network configuration with ifupdown (legacy)”</a>).</p>
</td>
</tr>
</table>
</div>
<p>The typical network connection method and connection path for a PC can be summarized as the following.</p>
<div class="table">
<a id="listofnetworkcondconnectionpaths"/>
<p class="title">
<strong>Table 5.3. List of network connection methods and connection paths</strong>
</p>
<div class="table-contents">
<table class="table" summary="List of network connection methods and connection paths" border="1">
<colgroup>
<col style="text-align: left"/>
<col style="text-align: left"/>
<col style="text-align: left"/>
</colgroup>
<thead>
<tr>
<th style="text-align: left">
PC
</th>
<th style="text-align: left">
connection method
</th>
<th style="text-align: left">
connection path
</th>
</tr>
</thead>
<tbody>
<tr>
<td style="text-align: left">
Serial port (<code class="literal">ppp0</code>)
</td>
<td style="text-align: left">
PPP
</td>
<td style="text-align: left">
⇔ <a class="ulink" href="http://en.wikipedia.org/wiki/Modem">modem</a> ⇔ POTS ⇔ dial-up access point ⇔ ISP
</td>
</tr>
<tr>
<td style="text-align: left">
Ethernet port (<code class="literal">eth0</code>)
</td>
<td style="text-align: left">
PPPoE/DHCP/Static
</td>
<td style="text-align: left">
⇔ BB-modem ⇔ BB service ⇔ BB access point ⇔ ISP
</td>
</tr>
<tr>
<td style="text-align: left">
Ethernet port (<code class="literal">eth0</code>)
</td>
<td style="text-align: left">
DHCP/Static
</td>
<td style="text-align: left">
⇔ LAN ⇔ BB-router with <a class="ulink" href="http://en.wikipedia.org/wiki/Network_address_translation">network address translation (NAT)</a> (⇔ BB-modem …)
</td>
</tr>
</tbody>
</table>
</div>
</div>
<br class="table-break"/>
<p>Here is the summary of configuration scripts for each connection method.</p>
<div class="table">
<a id="listofnetworkcononconfigurations"/>
<p class="title">
<strong>Table 5.4. List of network connection configurations</strong>
</p>
<div class="table-contents">
<table class="table" summary="List of network connection configurations" border="1">
<colgroup>
<col style="text-align: left"/>
<col style="text-align: left"/>
<col style="text-align: left"/>
</colgroup>
<thead>
<tr>
<th style="text-align: left">
connection method
</th>
<th style="text-align: left">
configuration
</th>
<th style="text-align: left">
backend package(s)
</th>
</tr>
</thead>
<tbody>
<tr>
<td style="text-align: left">
PPP
</td>
<td style="text-align: left"><code class="literal">pppconfig</code> to create deterministic chat
</td>
<td style="text-align: left"><code class="literal">pppconfig</code>, <code class="literal">ppp</code></td>
</tr>
<tr>
<td style="text-align: left">
PPP (alternative)
</td>
<td style="text-align: left"><code class="literal">wvdialconf</code> to create heuristic chat
</td>
<td style="text-align: left"><code class="literal">ppp</code>, <code class="literal">wvdial</code></td>
</tr>
<tr>
<td style="text-align: left">
PPPoE
</td>
<td style="text-align: left"><code class="literal">pppoeconf</code> to create deterministic chat
</td>
<td style="text-align: left"><code class="literal">pppoeconf</code>, <code class="literal">ppp</code></td>
</tr>
<tr>
<td style="text-align: left">
DHCP
</td>
<td style="text-align: left">
described in "<code class="literal">/etc/dhcp/dhclient.conf</code>"
</td>
<td style="text-align: left">
<code class="literal">isc-dhcp-client</code>
</td>
</tr>
<tr>
<td style="text-align: left">
static IP (IPv4)
</td>
<td style="text-align: left">
described in "<code class="literal">/etc/network/interfaces</code>"
</td>
<td style="text-align: left"><code class="literal">iproute</code> or <code class="literal">net-tools</code> (obsolete)
</td>
</tr>
<tr>
<td style="text-align: left">
static IP (IPv6)
</td>
<td style="text-align: left">
described in "<code class="literal">/etc/network/interfaces</code>"
</td>
<td style="text-align: left">
<code class="literal">iproute</code>
</td>
</tr>
</tbody>
</table>
</div>
</div>
<br class="table-break"/>
<p>The network connection acronyms mean the following.</p>
<div class="table">
<a id="listofnetworkconnectionacronyms"/>
<p class="title">
<strong>Table 5.5. List of network connection acronyms</strong>
</p>
<div class="table-contents">
<table class="table" summary="List of network connection acronyms" border="1">
<colgroup>
<col style="text-align: left"/>
<col style="text-align: left"/>
</colgroup>
<thead>
<tr>
<th style="text-align: left">
acronym
</th>
<th style="text-align: left">
meaning
</th>
</tr>
</thead>
<tbody>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://en.wikipedia.org/wiki/Plain_old_telephone_service">POTS</a>
</td>
<td style="text-align: left">
plain old telephone service
</td>
</tr>
<tr>
<td style="text-align: left">
BB
</td>
<td style="text-align: left">
<a class="ulink" href="http://en.wikipedia.org/wiki/Broadband">broadband</a>
</td>
</tr>
<tr>
<td style="text-align: left">
BB-service
</td>
<td style="text-align: left">
e.g., the digital subscriber line (DSL), the cable TV, or the fiber to the premises (FTTP)
</td>
</tr>
<tr>
<td style="text-align: left">
BB-modem
</td>
<td style="text-align: left">
e.g., <a class="ulink" href="http://en.wikipedia.org/wiki/DSL_modem">the DSL modem</a>, <a class="ulink" href="http://en.wikipedia.org/wiki/Cable_modem">the cable modem</a>, or <a class="ulink" href="http://en.wikipedia.org/wiki/FTTP">the optical network terminal (ONT)</a>
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://en.wikipedia.org/wiki/Local_area_network">LAN</a>
</td>
<td style="text-align: left">
local area network
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://en.wikipedia.org/wiki/Wide_area_network">WAN</a>
</td>
<td style="text-align: left">
wide area network
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://en.wikipedia.org/wiki/Dynamic_Host_Configuration_Protocol">DHCP</a>
</td>
<td style="text-align: left">
dynamic host configuration protocol
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://en.wikipedia.org/wiki/Point-to-Point_Protocol">PPP</a>
</td>
<td style="text-align: left">
point-to-point protocol
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://en.wikipedia.org/wiki/Point-to-Point_Protocol_over_Ethernet">PPPoE</a>
</td>
<td style="text-align: left">
point-to-point protocol over Ethernet
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://en.wikipedia.org/wiki/ISP">ISP</a>
</td>
<td style="text-align: left">
Internet service provider
</td>
</tr>
</tbody>
</table>
</div>
</div>
<br class="table-break"/>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<table border="0" summary="Note">
<tr>
<td rowspan="2" align="center" valign="top">
<img alt="[Note]" src="images/note.png"/>
</td>
<th align="left">Note</th>
</tr>
<tr>
<td align="left" valign="top">
<p>The WAN connection services via cable TV are generally served by DHCP or PPPoE. The ones by ADSL and FTTP are generally served by PPPoE. You have to consult your ISP for exact configuration requirements of the WAN connection.</p>
</td>
</tr>
</table>
</div>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<table border="0" summary="Note">
<tr>
<td rowspan="2" align="center" valign="top">
<img alt="[Note]" src="images/note.png"/>
</td>
<th align="left">Note</th>
</tr>
<tr>
<td align="left" valign="top">
<p>When BB-router is used to create home LAN environment, PCs on LAN are connected to the WAN via BB-router with <a class="ulink" href="http://en.wikipedia.org/wiki/Network_address_translation">network address translation (NAT)</a>. For such case, PC's network interfaces on the LAN are served by static IP or DHCP from the BB-router. BB-router must be configured to connect the WAN following the instruction by your ISP.</p>
</td>
</tr>
</table>
</div>
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="_the_dhcp_connection_with_the_ethernet"/>5.4.1. The DHCP connection with the Ethernet</h3>
</div>
</div>
</div>
<p>The typical modern home and small business network, i.e. LAN, are connected to the WAN (Internet) using some consumer grade broadband router. The LAN behind this router is usually served by the <a class="ulink" href="http://en.wikipedia.org/wiki/Dynamic_Host_Configuration_Protocol">dynamic host configuration protocol (DHCP)</a> server running on the router.</p>
<p>Just install the <code class="literal">isc-dhcp-client</code> package for the Ethernet served by the <a class="ulink" href="http://en.wikipedia.org/wiki/Dynamic_Host_Configuration_Protocol">dynamic host configuration protocol (DHCP)</a>.</p>
<p>See <span class="citerefentry"><span class="refentrytitle">dhclient.conf</span>(5)</span>.</p>
</div>
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="_the_static_ip_connection_with_the_ethernet"/>5.4.2. The static IP connection with the Ethernet</h3>
</div>
</div>
</div>
<p>No special action is needed for the Ethernet served by the static IP.</p>
</div>
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="_the_ppp_connection_with_pppconfig"/>5.4.3. The PPP connection with pppconfig</h3>
</div>
</div>
</div>
<p>The configuration script <code class="literal">pppconfig</code> configures the <a class="ulink" href="http://en.wikipedia.org/wiki/Point-to-Point_Protocol">PPP</a> connection interactively just by selecting the following.</p>
<div class="itemizedlist">
<ul class="itemizedlist">
<li class="listitem">
<p>
The telephone number
</p>
</li>
<li class="listitem">
<p>
The ISP user name
</p>
</li>
<li class="listitem">
<p>
The ISP password
</p>
</li>
<li class="listitem">
<p>
The port speed
</p>
</li>
<li class="listitem">
<p>
The modem communication port
</p>
</li>
<li class="listitem">
<p>
The authentication method
</p>
</li>
</ul>
</div>
<div class="table">
<a id="listofconfigurationwithpppconfig"/>
<p class="title">
<strong>Table 5.6. List of configuration files for the <a class="ulink" href="http://en.wikipedia.org/wiki/Point-to-Point_Protocol">PPP</a> connection with pppconfig</strong>
</p>
<div class="table-contents">
<table class="table" summary="List of configuration files for the PPP connection with pppconfig" border="1">
<colgroup>
<col style="text-align: left"/>
<col style="text-align: left"/>
</colgroup>
<thead>
<tr>
<th style="text-align: left">
file
</th>
<th style="text-align: left">
function
</th>
</tr>
</thead>
<tbody>
<tr>
<td style="text-align: left">
<code class="literal">/etc/ppp/peers/<isp_name></code>
</td>
<td style="text-align: left">
The <code class="literal">pppconfig</code> generated configuration file for <code class="literal">pppd</code> specific to <isp_name>
</td>
</tr>
<tr>
<td style="text-align: left">
<code class="literal">/etc/chatscripts/<isp_name></code>
</td>
<td style="text-align: left">
The <code class="literal">pppconfig</code> generated configuration file for <code class="literal">chat</code> specific to <isp_name>
</td>
</tr>
<tr>
<td style="text-align: left">
<code class="literal">/etc/ppp/options</code>
</td>
<td style="text-align: left">
The general execution parameter for <code class="literal">pppd</code>
</td>
</tr>
<tr>
<td style="text-align: left">
<code class="literal">/etc/ppp/pap-secret</code>
</td>
<td style="text-align: left">
Authentication data for the <a class="ulink" href="http://en.wikipedia.org/wiki/Password_authentication_protocol">PAP</a> (security risk)
</td>
</tr>
<tr>
<td style="text-align: left">
<code class="literal">/etc/ppp/chap-secret</code>
</td>
<td style="text-align: left">
Authentication data for the <a class="ulink" href="http://en.wikipedia.org/wiki/Challenge-handshake_authentication_protocol">CHAP</a> (more secure)
</td>
</tr>
</tbody>
</table>
</div>
</div>
<br class="table-break"/>
<div class="caution" style="margin-left: 0.5in; margin-right: 0.5in;">
<table border="0" summary="Caution">
<tr>
<td rowspan="2" align="center" valign="top">
<img alt="[Caution]" src="images/caution.png"/>
</td>
<th align="left">Caution</th>
</tr>
<tr>
<td align="left" valign="top">
<p>The "<isp_name>" value of "<code class="literal">provider</code>" is assumed if <code class="literal">pon</code> and <code class="literal">poff</code> commands are invoked without arguments.</p>
</td>
</tr>
</table>
</div>
<p>You can test configuration using low level network configuration tools as the following.</p>
<pre class="screen">$ sudo pon <isp_name>
...
$ sudo poff <isp_name></pre>
<p>See "<code class="literal">/usr/share/doc/ppp/README.Debian.gz</code>".</p>
</div>
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="_the_alternative_ppp_connection_with_wvdialconf"/>5.4.4. The alternative PPP connection with wvdialconf</h3>
</div>
</div>
</div>
<p>A different approach to using <span class="citerefentry"><span class="refentrytitle">pppd</span>(8)</span> is to run it from <span class="citerefentry"><span class="refentrytitle">wvdial</span>(1)</span> which comes in the <code class="literal">wvdial</code> package. Instead of <code class="literal">pppd</code> running <span class="citerefentry"><span class="refentrytitle">chat</span>(8)</span> to dial in and negotiate the connection, <code class="literal">wvdial</code> does the dialing and initial negotiating and then starts <code class="literal">pppd</code> to do the rest.</p>
<p>The configuration script <code class="literal">wvdialconf</code> configures the PPP connection interactively just by selecting the following.</p>
<div class="itemizedlist">
<ul class="itemizedlist">
<li class="listitem">
<p>
The telephone number
</p>
</li>
<li class="listitem">
<p>
The ISP user name
</p>
</li>
<li class="listitem">
<p>
The ISP password
</p>
</li>
</ul>
</div>
<p><code class="literal">wvdial</code> succeeds in making the connection in most cases and maintains authentication data list automatically.</p>
<div class="table">
<a id="listofconfiguratonwithwvdialconf"/>
<p class="title">
<strong>Table 5.7. List of configuration files for the PPP connection with wvdialconf</strong>
</p>
<div class="table-contents">
<table class="table" summary="List of configuration files for the PPP connection with wvdialconf" border="1">
<colgroup>
<col style="text-align: left"/>
<col style="text-align: left"/>
</colgroup>
<thead>
<tr>
<th style="text-align: left">
file
</th>
<th style="text-align: left">
function
</th>
</tr>
</thead>
<tbody>
<tr>
<td style="text-align: left">
<code class="literal">/etc/ppp/peers/wvdial</code>
</td>
<td style="text-align: left">
The <code class="literal">wvdialconf</code> generated configuration file for <code class="literal">pppd</code> specific to <code class="literal">wvdial</code>
</td>
</tr>
<tr>
<td style="text-align: left">
<code class="literal">/etc/wvdial.conf</code>
</td>
<td style="text-align: left">
The <code class="literal">wvdialconf</code> generated configuration file
</td>
</tr>
<tr>
<td style="text-align: left">
<code class="literal">/etc/ppp/options</code>
</td>
<td style="text-align: left">
The general execution parameter for <code class="literal">pppd</code>
</td>
</tr>
<tr>
<td style="text-align: left">
<code class="literal">/etc/ppp/pap-secret</code>
</td>
<td style="text-align: left">
Authentication data for the <a class="ulink" href="http://en.wikipedia.org/wiki/Password_authentication_protocol">PAP</a> (security risk)
</td>
</tr>
<tr>
<td style="text-align: left">
<code class="literal">/etc/ppp/chap-secret</code>
</td>
<td style="text-align: left">
Authentication data for the <a class="ulink" href="http://en.wikipedia.org/wiki/Challenge-handshake_authentication_protocol">CHAP</a> (more secure)
</td>
</tr>
</tbody>
</table>
</div>
</div>
<br class="table-break"/>
<p>You can test configuration using low level network configuration tools as the following.</p>
<pre class="screen">$ sudo wvdial
...
$ sudo killall wvdial</pre>
<p>See <span class="citerefentry"><span class="refentrytitle">wvdial</span>(1)</span> and <span class="citerefentry"><span class="refentrytitle">wvdial.conf</span>(5)</span>.</p>
</div>
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="_the_pppoe_connection_with_pppoeconf"/>5.4.5. The PPPoE connection with pppoeconf</h3>
</div>
</div>
</div>
<p>When your ISP serves you with PPPoE connection and you decide to connect your PC directly to the WAN, the network of your PC must be configured with the PPPoE. The PPPoE stand for PPP over Ethernet. The configuration script <code class="literal">pppoeconf</code> configures the PPPoE connection interactively.</p>
<p>The configuration files are the following.</p>
<div class="table">
<a id="listofconfigurationwithpppoeconf"/>
<p class="title">
<strong>Table 5.8. List of configuration files for the PPPoE connection with pppoeconf</strong>
</p>
<div class="table-contents">
<table class="table" summary="List of configuration files for the PPPoE connection with pppoeconf" border="1">
<colgroup>
<col style="text-align: left"/>
<col style="text-align: left"/>
</colgroup>
<thead>
<tr>
<th style="text-align: left">
file
</th>
<th style="text-align: left">
function
</th>
</tr>
</thead>
<tbody>
<tr>
<td style="text-align: left">
<code class="literal">/etc/ppp/peers/dsl-provider</code>
</td>
<td style="text-align: left">
The <code class="literal">pppoeconf</code> generated configuration file for <code class="literal">pppd</code> specific to <code class="literal">pppoe</code>
</td>
</tr>
<tr>
<td style="text-align: left">
<code class="literal">/etc/ppp/options</code>
</td>
<td style="text-align: left">
The general execution parameter for <code class="literal">pppd</code>
</td>
</tr>
<tr>
<td style="text-align: left">
<code class="literal">/etc/ppp/pap-secret</code>
</td>
<td style="text-align: left">
Authentication data for the <a class="ulink" href="http://en.wikipedia.org/wiki/Password_authentication_protocol">PAP</a> (security risk)
</td>
</tr>
<tr>
<td style="text-align: left">
<code class="literal">/etc/ppp/chap-secret</code>
</td>
<td style="text-align: left">
Authentication data for the <a class="ulink" href="http://en.wikipedia.org/wiki/Challenge-handshake_authentication_protocol">CHAP</a> (more secure)
</td>
</tr>
</tbody>
</table>
</div>
</div>
<br class="table-break"/>
<p>You can test configuration using low level network configuration tools as the following.</p>
<pre class="screen">$ sudo /sbin/ifconfig eth0 up
$ sudo pon dsl-provider
...
$ sudo poff dsl-provider
$ sudo /sbin/ifconfig eth0 down</pre>
<p>See "<code class="literal">/usr/share/doc/pppoeconf/README.Debian</code>".</p>
</div>
</div>
<div class="section">
<div class="titlepage">
<div>
<div>
<h2 class="title"><a id="_the_basic_network_configuration_with_ifupdown_legacy"/>5.5. The basic network configuration with ifupdown (legacy)</h2>
</div>
</div>
</div>
<p>The traditional <a class="ulink" href="http://en.wikipedia.org/wiki/Internet_Protocol_Suite">TCP/IP network</a> setup on the Debian system uses <code class="literal">ifupdown</code> package as a high level tool. There are 2 typical cases.</p>
<div class="itemizedlist">
<ul class="itemizedlist">
<li class="listitem">
<p>
For <span class="strong"><strong>dynamic IP</strong></span> system such as mobile PCs, you should setup TCP/IP network <span class="strong"><strong>with</strong></span> the <code class="literal">resolvconf</code> package and enable you to switch your network configuration easily (see <a class="xref" href="ch05.en.html#_the_network_interface_served_by_the_dhcp" title="5.5.4. The network interface served by the DHCP">Section 5.5.4, “The network interface served by the DHCP”</a>).
</p>
</li>
<li class="listitem">
<p>
For <span class="strong"><strong>static IP</strong></span> system such as servers, you should setup TCP/IP network <span class="strong"><strong>without</strong></span> the <code class="literal">resolvconf</code> package and keep your system simple (see <a class="xref" href="ch05.en.html#_the_network_interface_with_the_static_ip" title="5.5.5. The network interface with the static IP">Section 5.5.5, “The network interface with the static IP”</a>).
</p>
</li>
</ul>
</div>
<p>These traditional setup methods are quite useful if you wish to set up advanced configuration; find details in the following.</p>
<p>The <code class="literal">ifupdown</code> package provides the standardized framework for the high level network configuration in the Debian system. In this section, we learn the basic network configuration with <code class="literal">ifupdown</code> with simplified introduction and many typical examples.</p>
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="_the_command_syntax_simplified"/>5.5.1. The command syntax simplified</h3>
</div>
</div>
</div>
<p>The <code class="literal">ifupdown</code> package contains 2 commands: <span class="citerefentry"><span class="refentrytitle">ifup</span>(8)</span> and <span class="citerefentry"><span class="refentrytitle">ifdown</span>(8)</span>. They offer high level network configuration dictated by the configuration file "/etc/network/interfaces".</p>
<div class="table">
<a id="listofbasicnetwoandswithifupdown"/>
<p class="title">
<strong>Table 5.9. List of basic network configuration commands with ifupdown</strong>
</p>
<div class="table-contents">
<table class="table" summary="List of basic network configuration commands with ifupdown" border="1">
<colgroup>
<col style="text-align: left"/>
<col style="text-align: left"/>
</colgroup>
<thead>
<tr>
<th style="text-align: left">
command
</th>
<th style="text-align: left">
action
</th>
</tr>
</thead>
<tbody>
<tr>
<td style="text-align: left">
<code class="literal">ifup eth0</code>
</td>
<td style="text-align: left">
bring up a network interface <code class="literal">eth0</code> with the configuration <code class="literal">eth0</code> if "<code class="literal">iface eth0</code>" stanza exists
</td>
</tr>
<tr>
<td style="text-align: left">
<code class="literal">ifdown eth0</code>
</td>
<td style="text-align: left">
bring down a network interface <code class="literal">eth0</code> with the configuration <code class="literal">eth0</code> if "<code class="literal">iface eth0</code>" stanza exists
</td>
</tr>
</tbody>
</table>
</div>
</div>
<br class="table-break"/>
<div class="warning" style="margin-left: 0.5in; margin-right: 0.5in;">
<table border="0" summary="Warning">
<tr>
<td rowspan="2" align="center" valign="top">
<img alt="[Warning]" src="images/warning.png"/>
</td>
<th align="left">Warning</th>
</tr>
<tr>
<td align="left" valign="top">
<p>Do not use low level configuration tools such as <span class="citerefentry"><span class="refentrytitle">ifconfig</span>(8)</span> and <span class="citerefentry"><span class="refentrytitle">ip</span>(8)</span> commands to configure an interface in <span class="strong"><strong>up</strong></span> state.</p>
</td>
</tr>
</table>
</div>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<table border="0" summary="Note">
<tr>
<td rowspan="2" align="center" valign="top">
<img alt="[Note]" src="images/note.png"/>
</td>
<th align="left">Note</th>
</tr>
<tr>
<td align="left" valign="top">
<p>There is no command <code class="literal">ifupdown</code>.</p>
</td>
</tr>
</table>
</div>
</div>
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="_the_basic_syntax_of_etc_network_interfaces"/>5.5.2. The basic syntax of "/etc/network/interfaces"</h3>
</div>
</div>
</div>
<p>The key syntax of "<code class="literal">/etc/network/interfaces</code>" as explained in <span class="citerefentry"><span class="refentrytitle">interfaces</span>(5)</span> can be summarized as the following.</p>
<div class="table">
<a id="list-of-stanzas-in-eni"/>
<p class="title">
<strong>Table 5.10. List of stanzas in "<code class="literal">/etc/network/interfaces</code>"</strong>
</p>
<div class="table-contents">
<table class="table" summary="List of stanzas in "/etc/network/interfaces"" border="1">
<colgroup>
<col style="text-align: left"/>
<col style="text-align: left"/>
</colgroup>
<thead>
<tr>
<th style="text-align: left">
stanza
</th>
<th style="text-align: left">
meaning
</th>
</tr>
</thead>
<tbody>
<tr>
<td style="text-align: left">
"<code class="literal">auto <interface_name></code>"
</td>
<td style="text-align: left">
start interface <interface_name> upon start of the system
</td>
</tr>
<tr>
<td style="text-align: left">
"<code class="literal">allow-auto <interface_name></code>"
</td>
<td style="text-align: left">
, ,
</td>
</tr>
<tr>
<td style="text-align: left">
"<code class="literal">allow-hotplug <interface_name></code>"
</td>
<td style="text-align: left">
start interface <interface_name> when the kernel detects a hotplug event from the interface
</td>
</tr>
<tr>
<td style="text-align: left">
Lines started with "<code class="literal">iface <config_name> …</code>"
</td>
<td style="text-align: left">
define the network configuration <config_name>
</td>
</tr>
<tr>
<td style="text-align: left">
Lines started with "<code class="literal">mapping <interface_name_glob></code>"
</td>
<td style="text-align: left">
define mapping value of <config_name> for the matching <interface_name>
</td>
</tr>
<tr>
<td style="text-align: left">
A line starting with a hash "<code class="literal">#</code>"
</td>
<td style="text-align: left">
ignore as comments (end-of-line comments are <span class="strong"><strong>not</strong></span> supported)
</td>
</tr>
<tr>
<td style="text-align: left">
A line ending with a backslash "<code class="literal">\</code>"
</td>
<td style="text-align: left">
extend the configuration to the next line
</td>
</tr>
</tbody>
</table>
</div>
</div>
<br class="table-break"/>
<p>Lines started with <span class="strong"><strong><code class="literal">iface</code></strong></span> stanza has the following syntax.</p>
<pre class="screen">iface <config_name> <address_family> <method_name>
<option1> <value1>
<option2> <value2>
...</pre>
<p>For the basic configuration, the <span class="strong"><strong><code class="literal">mapping</code></strong></span> stanza is not used and you use the network interface name as the network configuration name (See <a class="xref" href="ch05.en.html#_the_mapping_stanza" title="5.6.5. The mapping stanza">Section 5.6.5, “The mapping stanza”</a>).</p>
<div class="warning" style="margin-left: 0.5in; margin-right: 0.5in;">
<table border="0" summary="Warning">
<tr>
<td rowspan="2" align="center" valign="top">
<img alt="[Warning]" src="images/warning.png"/>
</td>
<th align="left">Warning</th>
</tr>
<tr>
<td align="left" valign="top">
<p>Do not define duplicates of the "<code class="literal">iface</code>" stanza for a network interface in "<code class="literal">/etc/network/interfaces</code>".</p>
</td>
</tr>
</table>
</div>
</div>
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="_the_loopback_network_interface"/>5.5.3. The loopback network interface</h3>
</div>
</div>
</div>
<p>The following configuration entry in the "<code class="literal">/etc/network/interfaces</code>" file brings up the loopback network interface <code class="literal">lo</code> upon booting the system (via <span class="strong"><strong><code class="literal">auto</code></strong></span> stanza).</p>
<pre class="screen">auto lo
iface lo inet loopback</pre>
<p>This one always exists in the "<code class="literal">/etc/network/interfaces</code>" file.</p>
</div>
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="_the_network_interface_served_by_the_dhcp"/>5.5.4. The network interface served by the DHCP</h3>
</div>
</div>
</div>
<p>After preparing the system by <a class="xref" href="ch05.en.html#_the_dhcp_connection_with_the_ethernet" title="5.4.1. The DHCP connection with the Ethernet">Section 5.4.1, “The DHCP connection with the Ethernet”</a>, the network interface served by the DHCP is configured by creating the configuration entry in the "<code class="literal">/etc/network/interfaces</code>" file as the following.</p>
<pre class="screen">allow-hotplug eth0
iface eth0 inet dhcp</pre>
<p>When the Linux kernel detects the physical interface <code class="literal">eth0</code>, the <span class="strong"><strong><code class="literal">allow-hotplug</code></strong></span> stanza causes <code class="literal">ifup</code> to bring up the interface and the <span class="strong"><strong><code class="literal">iface</code></strong></span> stanza causes <code class="literal">ifup</code> to use DHCP to configure the interface.</p>
</div>
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="_the_network_interface_with_the_static_ip"/>5.5.5. The network interface with the static IP</h3>
</div>
</div>
</div>
<p>The network interface served by the static IP is configured by creating the configuration entry in the "<code class="literal">/etc/network/interfaces</code>" file as the following.</p>
<pre class="screen">allow-hotplug eth0
iface eth0 inet static
address 192.168.11.100
netmask 255.255.255.0
gateway 192.168.11.1
dns-domain example.com
dns-nameservers 192.168.11.1</pre>
<p>When the Linux kernel detects the physical interface <code class="literal">eth0</code>, the <span class="strong"><strong><code class="literal">allow-hotplug</code></strong></span> stanza causes <code class="literal">ifup</code> to bring up the interface and the <span class="strong"><strong><code class="literal">iface</code></strong></span> stanza causes <code class="literal">ifup</code> to use the static IP to configure the interface.</p>
<p>Here, I assumed the following.</p>
<div class="itemizedlist">
<ul class="itemizedlist">
<li class="listitem">
<p>
IP address range of the LAN network: <code class="literal">192.168.11.0</code> - <code class="literal">192.168.11.255</code>
</p>
</li>
<li class="listitem">
<p>
IP address of the gateway: <code class="literal">192.168.11.1</code>
</p>
</li>
<li class="listitem">
<p>
IP address of the PC: <code class="literal">192.168.11.100</code>
</p>
</li>
<li class="listitem">
<p>
The <code class="literal">resolvconf</code> package: installed
</p>
</li>
<li class="listitem">
<p>
The domain name: "<code class="literal">example.com</code>"
</p>
</li>
<li class="listitem">
<p>
IP address of the DNS server: <code class="literal">192.168.11.1</code>
</p>
</li>
</ul>
</div>
<p>When the <code class="literal">resolvconf</code> package is not installed, DNS related configuration needs to be done manually by editing the "<code class="literal">/etc/resolv.conf</code>" as the following.</p>
<pre class="screen">nameserver 192.168.11.1
domain example.com</pre>
<div class="caution" style="margin-left: 0.5in; margin-right: 0.5in;">
<table border="0" summary="Caution">
<tr>
<td rowspan="2" align="center" valign="top">
<img alt="[Caution]" src="images/caution.png"/>
</td>
<th align="left">Caution</th>
</tr>
<tr>
<td align="left" valign="top">
<p>The IP addresses used in the above example are not meant to be copied literally. You have to adjust IP numbers to your actual network configuration.</p>
</td>
</tr>
</table>
</div>
</div>
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="_the_basics_of_wireless_lan_interface"/>5.5.6. The basics of wireless LAN interface</h3>
</div>
</div>
</div>
<p>The <a class="ulink" href="http://en.wikipedia.org/wiki/Wireless_LAN">wireless LAN (WLAN for short)</a> provides the fast wireless connectivity through the spread-spectrum communication of unlicensed radio bands based on the set of standards called <a class="ulink" href="http://en.wikipedia.org/wiki/IEEE_802.11">IEEE 802.11</a>.</p>
<p>The WLAN interfaces are almost like normal Ethernet interfaces but require some network ID and encryption key data to be provided when they are initialized. Their high level network tools are exactly the same as that of Ethernet interfaces except interface names are a bit different like <code class="literal">eth1</code>, <code class="literal">wlan0</code>, <code class="literal">ath0</code>, <code class="literal">wifi0</code>, … depending on the kernel drivers used.</p>
<div class="tip" style="margin-left: 0.5in; margin-right: 0.5in;">
<table border="0" summary="Tip">
<tr>
<td rowspan="2" align="center" valign="top">
<img alt="[Tip]" src="images/tip.png"/>
</td>
<th align="left">Tip</th>
</tr>
<tr>
<td align="left" valign="top">
<p>The <code class="literal">wmaster0</code> device is the master device which is an internal device used only by <a class="ulink" href="http://en.wikipedia.org/wiki/SoftMAC">SoftMAC</a> with new <a class="ulink" href="http://linuxwireless.org/">mac80211 API of Linux</a>.</p>
</td>
</tr>
</table>
</div>
<p>Here are some keywords to remember for the WLAN.</p>
<div class="table">
<a id="listofacronymsforwlan"/>
<p class="title">
<strong>Table 5.11. List of acronyms for WLAN</strong>
</p>
<div class="table-contents">
<table class="table" summary="List of acronyms for WLAN" border="1">
<colgroup>
<col style="text-align: left"/>
<col style="text-align: left"/>
<col style="text-align: left"/>
</colgroup>
<thead>
<tr>
<th style="text-align: left">
acronym
</th>
<th style="text-align: left">
full word
</th>
<th style="text-align: left">
meaning
</th>
</tr>
</thead>
<tbody>
<tr>
<td style="text-align: left">
NWID
</td>
<td style="text-align: left">
Network ID
</td>
<td style="text-align: left">
16 bit network ID used by pre-802.11 <a class="ulink" href="http://en.wikipedia.org/wiki/WaveLAN">WaveLAN</a> network (very deprecated)
</td>
</tr>
<tr>
<td style="text-align: left">
(E)SSID
</td>
<td style="text-align: left">
(Extended) <a class="ulink" href="http://en.wikipedia.org/wiki/Service_set_identifier">Service Set Identifier</a>
</td>
<td style="text-align: left">
network name of the <a class="ulink" href="http://en.wikipedia.org/wiki/Wireless_access_point">Wireless Access Points (APs)</a> interconnected to form an integrated <a class="ulink" href="http://en.wikipedia.org/wiki/IEEE_802.11">802.11 wireless LAN</a>, Domain ID
</td>
</tr>
<tr>
<td style="text-align: left">
WEP, (WEP2)
</td>
<td style="text-align: left">
<a class="ulink" href="http://en.wikipedia.org/wiki/Wired_Equivalent_Privacy">Wired Equivalent Privacy</a>
</td>
<td style="text-align: left">
1st generation 64-bit (128-bit) wireless encryption standard with 40-bit key (deprecated)
</td>
</tr>
<tr>
<td style="text-align: left">
WPA
</td>
<td style="text-align: left">
<a class="ulink" href="http://en.wikipedia.org/wiki/Wi-Fi_Protected_Access">Wi-Fi Protected Access</a>
</td>
<td style="text-align: left">
2nd generation wireless encryption standard (most of 802.11i), compatible with WEP
</td>
</tr>
<tr>
<td style="text-align: left">
WPA2
</td>
<td style="text-align: left">
<a class="ulink" href="http://en.wikipedia.org/wiki/IEEE_802.11i">Wi-Fi Protected Access 2</a>
</td>
<td style="text-align: left">
3rd generation wireless encryption standard (full 802.11i), non-compatible with WEP
</td>
</tr>
</tbody>
</table>
</div>
</div>
<br class="table-break"/>
<p>The actual choice of protocol is usually limited by the wireless router you deploy.</p>
</div>
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="_the_wireless_lan_interface_with_wpa_wpa2"/>5.5.7. The wireless LAN interface with WPA/WPA2</h3>
</div>
</div>
</div>
<p>You need to install the <code class="literal">wpasupplicant</code> package to support the WLAN with the new WPA/WPA2.</p>
<p>In case of the <a class="ulink" href="http://en.wikipedia.org/wiki/Dynamic_Host_Configuration_Protocol">DHCP</a> served IP on WLAN connection, the "<code class="literal">/etc/network/interfaces</code>" file entry should be as the following.</p>
<pre class="screen">allow-hotplug ath0
iface ath0 inet dhcp
wpa-ssid homezone
# hexadecimal psk is encoded from a plaintext passphrase
wpa-psk 000102030405060708090a0b0c0d0e0f101112131415161718191a1b1c1d1e1f</pre>
<p>See "<code class="literal">/usr/share/doc/wpasupplicant/README.modes.gz</code>".</p>
</div>
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="_the_wireless_lan_interface_with_wep"/>5.5.8. The wireless LAN interface with WEP</h3>
</div>
</div>
</div>
<p>You need to install the <code class="literal">wireless-tools</code> package to support the WLAN with the old WEP. (Your consumer grade router may still be using this insecure infrastructure but this is better than nothing.)</p>
<div class="caution" style="margin-left: 0.5in; margin-right: 0.5in;">
<table border="0" summary="Caution">
<tr>
<td rowspan="2" align="center" valign="top">
<img alt="[Caution]" src="images/caution.png"/>
</td>
<th align="left">Caution</th>
</tr>
<tr>
<td align="left" valign="top">
<p>Please note that your network traffic on WLAN with WEP may be sniffed by others.</p>
</td>
</tr>
</table>
</div>
<p>In case of the <a class="ulink" href="http://en.wikipedia.org/wiki/Dynamic_Host_Configuration_Protocol">DHCP</a> served IP on WLAN connection, the "<code class="literal">/etc/network/interfaces</code>" file entry should be as the following.</p>
<pre class="screen">allow-hotplug eth0
iface eth0 inet dhcp
wireless-essid Home
wireless-key1 0123-4567-89ab-cdef
wireless-key2 12345678
wireless-key3 s:password
wireless-defaultkey 2
wireless-keymode open</pre>
<p>See "<code class="literal">/usr/share/doc/wireless-tools/README.Debian</code>".</p>
</div>
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="_the_ppp_connection"/>5.5.9. The PPP connection</h3>
</div>
</div>
</div>
<p>You need to configure the PPP connection first as described before (see <a class="xref" href="ch05.en.html#_the_ppp_connection_with_pppconfig" title="5.4.3. The PPP connection with pppconfig">Section 5.4.3, “The PPP connection with pppconfig”</a>). Then, add the "<code class="literal">/etc/network/interfaces</code>" file entry for the primary PPP device <code class="literal">ppp0</code> as the following.</p>
<pre class="screen">iface ppp0 inet ppp
provider <isp_name></pre>
</div>
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="_the_alternative_ppp_connection"/>5.5.10. The alternative PPP connection</h3>
</div>
</div>
</div>
<p>You need to configure the alternative PPP connection with <code class="literal">wvdial</code> first as described before (see <a class="xref" href="ch05.en.html#_the_alternative_ppp_connection_with_wvdialconf" title="5.4.4. The alternative PPP connection with wvdialconf">Section 5.4.4, “The alternative PPP connection with wvdialconf”</a>). Then, add the "<code class="literal">/etc/network/interfaces</code>" file entry for the primary PPP device <code class="literal">ppp0</code> as the following.</p>
<pre class="screen">iface ppp0 inet wvdial</pre>
</div>
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="_the_pppoe_connection"/>5.5.11. The PPPoE connection</h3>
</div>
</div>
</div>
<p>For PC connected directly to the WAN served by the PPPoE, you need to configure system with the PPPoE connection as described before (see <a class="xref" href="ch05.en.html#_the_pppoe_connection_with_pppoeconf" title="5.4.5. The PPPoE connection with pppoeconf">Section 5.4.5, “The PPPoE connection with pppoeconf”</a>). Then, add the "<code class="literal">/etc/network/interfaces</code>" file entry for the primary PPPoE device <code class="literal">eth0</code> as the following.</p>
<pre class="screen">allow-hotplug eth0
iface eth0 inet manual
pre-up /sbin/ifconfig eth0 up
up ifup ppp0=dsl
down ifdown ppp0=dsl
post-down /sbin/ifconfig eth0 down
# The following is used internally only
iface dsl inet ppp
provider dsl-provider</pre>
</div>
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="_the_network_configuration_state_of_ifupdown"/>5.5.12. The network configuration state of ifupdown</h3>
</div>
</div>
</div>
<p>The "<code class="literal">/etc/network/run/ifstate</code>" file stores the <span class="strong"><strong>intended</strong></span> network configuration states for all the currently active network interfaces managed by the <code class="literal">ifupdown</code> package. Unfortunately, even if the <code class="literal">ifupdown</code> system fails to bring up the interface as intended, the "<code class="literal">/etc/network/run/ifstate</code>" file lists it active.</p>
<p>Unless the output of the <span class="citerefentry"><span class="refentrytitle">ifconfig</span>(8)</span> command for an interface does not have a line like following example, it can not be used as a part of <a class="ulink" href="http://en.wikipedia.org/wiki/IPv4">IPV4 network</a>.</p>
<pre class="screen"> inet addr:192.168.11.2 Bcast:192.168.11.255 Mask:255.255.255.0</pre>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<table border="0" summary="Note">
<tr>
<td rowspan="2" align="center" valign="top">
<img alt="[Note]" src="images/note.png"/>
</td>
<th align="left">Note</th>
</tr>
<tr>
<td align="left" valign="top">
<p>For the Ethernet device connected to the PPPoE, the output of the <span class="citerefentry"><span class="refentrytitle">ifconfig</span>(8)</span> command lacks a line which looks like above example.</p>
</td>
</tr>
</table>
</div>
</div>
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="_the_basic_network_reconfiguration"/>5.5.13. The basic network reconfiguration</h3>
</div>
</div>
</div>
<p>When you try to reconfigure the interface, e.g. <code class="literal">eth0</code>, you must disable it first with the "<span class="strong"><strong><code class="literal">sudo ifdown eth0</code></strong></span>" command. This removes the entry of <code class="literal">eth0</code> from the "<code class="literal">/etc/network/run/ifstate</code>" file. (This may result in some error message if <code class="literal">eth0</code> is not active or it is configured improperly previously. So far, it seems to be safe to do this for the simple single user work station at any time.)</p>
<p>You are now free to rewrite the "<code class="literal">/etc/network/interfaces</code>" contents as needed to reconfigure the network interface, <code class="literal">eth0</code>.</p>
<p>Then, you can reactivate <code class="literal">eth0</code> with the "<span class="strong"><strong><code class="literal">sudo ifup eth0</code></strong></span>" command.</p>
<div class="tip" style="margin-left: 0.5in; margin-right: 0.5in;">
<table border="0" summary="Tip">
<tr>
<td rowspan="2" align="center" valign="top">
<img alt="[Tip]" src="images/tip.png"/>
</td>
<th align="left">Tip</th>
</tr>
<tr>
<td align="left" valign="top">
<p>You can (re)initialize the network interface simply by "<span class="strong"><strong><code class="literal">sudo ifdown eth0;sudo ifup eth0</code></strong></span>".</p>
</td>
</tr>
</table>
</div>
</div>
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="_the_ifupdown_extra_package"/>5.5.14. The ifupdown-extra package</h3>
</div>
</div>
</div>
<p>The <code class="literal">ifupdown-extra</code> package provides easy network connection tests for use with the <code class="literal">ifupdown</code> package.</p>
<div class="itemizedlist">
<ul class="itemizedlist">
<li class="listitem">
<p>
The <span class="citerefentry"><span class="refentrytitle">network-test</span>(1)</span> command can be used from the shell.
</p>
</li>
<li class="listitem">
<p>
The automatic scripts are run for each <code class="literal">ifup</code> command execution.
</p>
</li>
</ul>
</div>
<p>The <code class="literal">network-test</code> command frees you from the execution of cumbersome low level commands to analyze the network problem.</p>
<p>The automatic scripts are installed in "<code class="literal">/etc/network/*/</code>" and perform the following.</p>
<div class="itemizedlist">
<ul class="itemizedlist">
<li class="listitem">
<p>
Check the network cable connection
</p>
</li>
<li class="listitem">
<p>
Check duplicate use of IP address
</p>
</li>
<li class="listitem">
<p>
Setup system's static routes based on the "<code class="literal">/etc/network/routes</code>" definition
</p>
</li>
<li class="listitem">
<p>
Check if network gateway is reachable
</p>
</li>
<li class="listitem">
<p>
Record results in the "<code class="literal">/var/log/syslog</code>" file
</p>
</li>
</ul>
</div>
<p>This syslog record is quite useful for administration of the network problem on the remote system.</p>
<div class="tip" style="margin-left: 0.5in; margin-right: 0.5in;">
<table border="0" summary="Tip">
<tr>
<td rowspan="2" align="center" valign="top">
<img alt="[Tip]" src="images/tip.png"/>
</td>
<th align="left">Tip</th>
</tr>
<tr>
<td align="left" valign="top">
<p>The automatic behavior of the <code class="literal">ifupdown-extra</code> package is configurable with the "<code class="literal">/etc/default/network-test</code>". Some of these automatic checks slow down the system boot-up a little bit since it takes some time to listen for <a class="ulink" href="http://en.wikipedia.org/wiki/Address_Resolution_Protocol">ARP</a> replies.</p>
</td>
</tr>
</table>
</div>
</div>
</div>
<div class="section">
<div class="titlepage">
<div>
<div>
<h2 class="title"><a id="_the_advanced_network_configuration_with_ifupdown_legacy"/>5.6. The advanced network configuration with ifupdown (legacy)</h2>
</div>
</div>
</div>
<p>The functionality of the <code class="literal">ifupdown</code> package can be improved beyond what was described in <a class="xref" href="ch05.en.html#_the_basic_network_configuration_with_ifupdown_legacy" title="5.5. The basic network configuration with ifupdown (legacy)">Section 5.5, “The basic network configuration with ifupdown (legacy)”</a> with the advanced knowledge.</p>
<p>The functionalities described here are completely optional. I, being lazy and minimalist, rarely bother to use these.</p>
<div class="caution" style="margin-left: 0.5in; margin-right: 0.5in;">
<table border="0" summary="Caution">
<tr>
<td rowspan="2" align="center" valign="top">
<img alt="[Caution]" src="images/caution.png"/>
</td>
<th align="left">Caution</th>
</tr>
<tr>
<td align="left" valign="top">
<p>If you could not set up network connection by information in <a class="xref" href="ch05.en.html#_the_basic_network_configuration_with_ifupdown_legacy" title="5.5. The basic network configuration with ifupdown (legacy)">Section 5.5, “The basic network configuration with ifupdown (legacy)”</a>, you make situation worse by using information below.</p>
</td>
</tr>
</table>
</div>
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="_the_ifplugd_package"/>5.6.1. The ifplugd package</h3>
</div>
</div>
</div>
<p>The <code class="literal">ifplugd</code> package is an older automatic network configuration tool which can manage only Ethernet connections. This solves unplugged/replugged Ethernet cable issues for mobile PC etc. If you have <a class="ulink" href="http://en.wikipedia.org/wiki/NetworkManager">NetworkManager</a> or <a class="ulink" href="http://en.wikipedia.org/wiki/Wicd_(Linux_Network_Manager)">Wicd</a> (see <a class="xref" href="ch05.en.html#_the_modern_network_configuration_for_desktop" title="5.2. The modern network configuration for desktop">Section 5.2, “The modern network configuration for desktop”</a>) installed, you do not need this package.</p>
<p>This package runs a <a class="ulink" href="http://en.wikipedia.org/wiki/Daemon_(computer_software)">daemon</a> and replaces <span class="strong"><strong>auto</strong></span> or <span class="strong"><strong>allow-hotplug</strong></span> functionalities (see <a class="xref" href="ch05.en.html#list-of-stanzas-in-eni" title="Table 5.10. List of stanzas in "/etc/network/interfaces"">Table 5.10, “List of stanzas in "<code class="literal">/etc/network/interfaces</code>"”</a>) and starts interfaces upon their connection to the network.</p>
<p>Here is how to use the <code class="literal">ifplugd</code> package for the internal Ethernet port, e.g. <code class="literal">eth0</code>.</p>
<div class="orderedlist">
<ol class="orderedlist">
<li class="listitem">
<p>
Remove stanza in "<code class="literal">/etc/network/interfaces</code>": "<code class="literal">auto eth0</code>" or "<code class="literal">allow-hotplug eth0</code>".
</p>
</li>
<li class="listitem">
<p>
Keep stanza in "<code class="literal">/etc/network/interfaces</code>": "<code class="literal">iface eth0 inet …</code>" and "<code class="literal">mapping …</code>".
</p>
</li>
<li class="listitem">
<p>
Install the <code class="literal">ifplugd</code> package.
</p>
</li>
<li class="listitem">
<p>
Run "<code class="literal">sudo dpkg-reconfigure ifplugd</code>".
</p>
</li>
<li class="listitem">
<p>
Put <code class="literal">eth0</code> as the "static interfaces to be watched by ifplugd".
</p>
</li>
</ol>
</div>
<p>Now, the network reconfiguration works as you desire.</p>
<div class="itemizedlist">
<ul class="itemizedlist">
<li class="listitem">
<p>
Upon power-on or upon hardware discovery, the interface is not brought up by itself.
</p>
<div class="itemizedlist">
<ul class="itemizedlist">
<li class="listitem">
<p>
Quick boot process without the long DHCP timeout.
</p>
</li>
<li class="listitem">
<p>
No funny activated interface without proper IPv4 address (see <a class="xref" href="ch05.en.html#_the_network_configuration_state_of_ifupdown" title="5.5.12. The network configuration state of ifupdown">Section 5.5.12, “The network configuration state of ifupdown”</a>).
</p>
</li>
</ul>
</div>
</li>
<li class="listitem">
<p>
Upon finding the Ethernet cable, the interface is brought up.
</p>
</li>
<li class="listitem">
<p>
Upon some time after unplugging the Ethernet cable, the interface is brought down automatically.
</p>
</li>
<li class="listitem">
<p>
Upon plugging in another Ethernet cable, the interface is brought up under the new network environment.
</p>
</li>
</ul>
</div>
<div class="tip" style="margin-left: 0.5in; margin-right: 0.5in;">
<table border="0" summary="Tip">
<tr>
<td rowspan="2" align="center" valign="top">
<img alt="[Tip]" src="images/tip.png"/>
</td>
<th align="left">Tip</th>
</tr>
<tr>
<td align="left" valign="top">
<p>The arguments for the <span class="citerefentry"><span class="refentrytitle">ifplugd</span>(8)</span> command can set its behaviors such as the delay for reconfiguring interfaces.</p>
</td>
</tr>
</table>
</div>
</div>
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="_the_ifmetric_package"/>5.6.2. The ifmetric package</h3>
</div>
</div>
</div>
<p>The <code class="literal">ifmetric</code> package enables us to manipulate metrics of routes a posteriori even for DHCP.</p>
<p>The following sets the <code class="literal">eth0</code> interface to be preferred over the <code class="literal">wlan0</code> interface.</p>
<div class="orderedlist">
<ol class="orderedlist">
<li class="listitem">
<p>
Install the <code class="literal">ifmetric</code> package.
</p>
</li>
<li class="listitem">
<p>
Add an option line with "<code class="literal">metric 0</code>" just below the "<code class="literal">iface eth0 inet dhcp</code>" line in "<code class="literal">/etc/network/interfaces</code>".
</p>
</li>
<li class="listitem">
<p>
Add an option line with "<code class="literal">metric 1</code>" just below the "<code class="literal">iface wlan0 inet dhcp</code>" line in "<code class="literal">/etc/network/interfaces</code>".
</p>
</li>
</ol>
</div>
<p>The metric 0 means the highest priority route and is the default one. The larger metric value means lower priority routes. The IP address of the active interface with the lowest metric value becomes the originating one. See <span class="citerefentry"><span class="refentrytitle">ifmetric</span>(8)</span>.</p>
</div>
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="_the_virtual_interface"/>5.6.3. The virtual interface</h3>
</div>
</div>
</div>
<p>A single physical Ethernet interface can be configured as multiple virtual interfaces with different IP addresses. Usually the purpose is to connect an interface to several IP subnetworks. For example, IP address based virtual web hosting by a single network interface is one such application.</p>
<p>For example, let's suppose the following.</p>
<div class="itemizedlist">
<ul class="itemizedlist">
<li class="listitem">
<p>
A single Ethernet interface on your host is connected to a Ethernet hub (not to the broadband router).
</p>
</li>
<li class="listitem">
<p>
The Ethernet hub is connected to both the Internet and LAN network.
</p>
</li>
<li class="listitem">
<p>
The LAN network uses subnet <code class="literal">192.168.0.x/24</code>.
</p>
</li>
<li class="listitem">
<p>
Your host uses DHCP served IP address with the physical interface <code class="literal">eth0</code> for the Internet.
</p>
</li>
<li class="listitem">
<p>
Your host uses <code class="literal">192.168.0.1</code> with the virtual interface <code class="literal">eth0:0</code> for the LAN.
</p>
</li>
</ul>
</div>
<p>The following stanzas in "<code class="literal">/etc/network/interfaces</code>" configure your network.</p>
<pre class="screen">iface eth0 inet dhcp
metric 0
iface eth0:0 inet static
address 192.168.0.1
netmask 255.255.255.0
network 192.168.0.0
metric 1</pre>
<div class="caution" style="margin-left: 0.5in; margin-right: 0.5in;">
<table border="0" summary="Caution">
<tr>
<td rowspan="2" align="center" valign="top">
<img alt="[Caution]" src="images/caution.png"/>
</td>
<th align="left">Caution</th>
</tr>
<tr>
<td align="left" valign="top">
<p>Although this configuration example with <a class="ulink" href="http://en.wikipedia.org/wiki/Network_address_translation">network address translation (NAT)</a> using <a class="ulink" href="http://en.wikipedia.org/wiki/Netfilter">netfilter/iptables</a> (see <a class="xref" href="ch05.en.html#_netfilter_infrastructure" title="5.9. Netfilter infrastructure">Section 5.9, “Netfilter infrastructure”</a>) can provide cheap router for the LAN with only single interface, there is no real firewall capability with such set up. You should use 2 physical interfaces with NAT to secure the local network from the Internet.</p>
</td>
</tr>
</table>
</div>
</div>
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="_the_advanced_command_syntax"/>5.6.4. The advanced command syntax</h3>
</div>
</div>
</div>
<p>The <code class="literal">ifupdown</code> package offers advanced network configuration using the <span class="strong"><strong>network configuration</strong></span> name and the <span class="strong"><strong>network interface</strong></span> name. I use a terminology being slightly different from the one used in <span class="citerefentry"><span class="refentrytitle">ifup</span>(8)</span> and <span class="citerefentry"><span class="refentrytitle">interfaces</span>(5)</span>.</p>
<div class="table">
<a id="listofterminologornetworkdevices"/>
<p class="title">
<strong>Table 5.12. List of terminology for network devices</strong>
</p>
<div class="table-contents">
<table class="table" summary="List of terminology for network devices" border="1">
<colgroup>
<col style="text-align: left"/>
<col style="text-align: left"/>
<col style="text-align: left"/>
<col style="text-align: left"/>
</colgroup>
<thead>
<tr>
<th style="text-align: left">
manpage terminology
</th>
<th style="text-align: left">
my terminology
</th>
<th style="text-align: left">
examples in the following text
</th>
<th style="text-align: left">
description
</th>
</tr>
</thead>
<tbody>
<tr>
<td style="text-align: left"><span class="strong"><strong>physical interface</strong></span> name
</td>
<td style="text-align: left"><span class="strong"><strong>network interface</strong></span> name
</td>
<td style="text-align: left"><code class="literal">lo</code>, <code class="literal">eth0</code>, <code class="literal"><interface_name></code></td>
<td style="text-align: left">
name given by the Linux kernel (using <code class="literal">udev</code> mechanism)
</td>
</tr>
<tr>
<td style="text-align: left"><span class="strong"><strong>logical interface</strong></span> name
</td>
<td style="text-align: left"><span class="strong"><strong>network configuration</strong></span> name
</td>
<td style="text-align: left"><code class="literal">config1</code>, <code class="literal">config2</code>, <code class="literal"><config_name></code></td>
<td style="text-align: left">
name token following <span class="strong"><strong><code class="literal">iface</code></strong></span> in the "<code class="literal">/etc/network/interfaces</code>"
</td>
</tr>
</tbody>
</table>
</div>
</div>
<br class="table-break"/>
<p>Basic network configuration commands in <a class="xref" href="ch05.en.html#_the_command_syntax_simplified" title="5.5.1. The command syntax simplified">Section 5.5.1, “The command syntax simplified”</a> require the <span class="strong"><strong>network configuration</strong></span> name token of the <span class="strong"><strong><code class="literal">iface</code></strong></span> stanza to match the <span class="strong"><strong>network interface</strong></span> name in the "<code class="literal">/etc/network/interfaces</code>".</p>
<p>Advanced network configuration commands enables separation of the <span class="strong"><strong>network configuration</strong></span> name and the <span class="strong"><strong>network interface</strong></span> name in the "<code class="literal">/etc/network/interfaces</code>" as the following.</p>
<div class="table">
<a id="listofadvancedneandswithifupdown"/>
<p class="title">
<strong>Table 5.13. List of advanced network configuration commands with ifupdown</strong>
</p>
<div class="table-contents">
<table class="table" summary="List of advanced network configuration commands with ifupdown" border="1">
<colgroup>
<col style="text-align: left"/>
<col style="text-align: left"/>
</colgroup>
<thead>
<tr>
<th style="text-align: left">
command
</th>
<th style="text-align: left">
action
</th>
</tr>
</thead>
<tbody>
<tr>
<td style="text-align: left">
<code class="literal">ifup eth0=config1</code>
</td>
<td style="text-align: left">
bring up a network interface <code class="literal">eth0</code> with the configuration <code class="literal">config1</code>
</td>
</tr>
<tr>
<td style="text-align: left">
<code class="literal">ifdown eth0=config1</code>
</td>
<td style="text-align: left">
bring down a network interface <code class="literal">eth0</code> with the configuration <code class="literal">config1</code>
</td>
</tr>
<tr>
<td style="text-align: left">
<code class="literal">ifup eth0</code>
</td>
<td style="text-align: left">
bring up a network interface <code class="literal">eth0</code> with the configuration selected by <span class="strong"><strong><code class="literal">mapping</code></strong></span> stanza
</td>
</tr>
<tr>
<td style="text-align: left">
<code class="literal">ifdown eth0</code>
</td>
<td style="text-align: left">
bring down a network interface <code class="literal">eth0</code> with the configuration selected by <span class="strong"><strong><code class="literal">mapping</code></strong></span> stanza
</td>
</tr>
</tbody>
</table>
</div>
</div>
<br class="table-break"/>
</div>
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="_the_mapping_stanza"/>5.6.5. The mapping stanza</h3>
</div>
</div>
</div>
<p>We skipped explaining the <span class="strong"><strong><code class="literal">mapping</code></strong></span> stanza in the "<code class="literal">/etc/network/interfaces</code>" in <a class="xref" href="ch05.en.html#_the_basic_syntax_of_etc_network_interfaces" title="5.5.2. The basic syntax of "/etc/network/interfaces"">Section 5.5.2, “The basic syntax of "/etc/network/interfaces"”</a> to avoid complication. This stanza has the following syntax.</p>
<pre class="screen">mapping <interface_name_glob>
script <script_name>
map <script_input1>
map <script_input2>
map ...</pre>
<p>This provides advanced features to the "<code class="literal">/etc/network/interfaces</code>" file by automating the choice of the configuration with the mapping script specified by <code class="literal"><script_name></code>.</p>
<p>Let's follow the execution of the following.</p>
<pre class="screen">$ sudo ifup eth0</pre>
<p>When the "<code class="literal"><interface_name_glob></code>" matches "<code class="literal">eth0</code>", this execution produces the execution of the following command to configure <code class="literal">eth0</code> automatically.</p>
<pre class="screen">$ sudo ifup eth0=$(echo -e '<script_input1> \n <script_input2> \n ...' | <script_name> eth0)</pre>
<p>Here, script input lines with "<code class="literal">map</code>" are optional and can be repeated.</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<table border="0" summary="Note">
<tr>
<td rowspan="2" align="center" valign="top">
<img alt="[Note]" src="images/note.png"/>
</td>
<th align="left">Note</th>
</tr>
<tr>
<td align="left" valign="top">
<p>The glob for <span class="strong"><strong><code class="literal">mapping</code></strong></span> stanza works like shell filename glob (see <a class="xref" href="ch01.en.html#_shell_glob" title="1.5.6. Shell glob">Section 1.5.6, “Shell glob”</a>).</p>
</td>
</tr>
</table>
</div>
</div>
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="_the_manually_switchable_network_configuration"/>5.6.6. The manually switchable network configuration</h3>
</div>
</div>
</div>
<p>Here is how to switch manually among several network configurations without rewriting the "<code class="literal">/etc/network/interfaces</code>" file as in <a class="xref" href="ch05.en.html#_the_basic_network_reconfiguration" title="5.5.13. The basic network reconfiguration">Section 5.5.13, “The basic network reconfiguration”</a> .</p>
<p>For all the network configuration you need to access, you create a separate stanza in "<code class="literal">/etc/network/interfaces</code>" file as the following.</p>
<pre class="screen">auto lo
iface lo inet loopback
iface config1 inet dhcp
iface config2 inet static
address 192.168.11.100
netmask 255.255.255.0
gateway 192.168.11.1
dns-domain example.com
dns-nameservers 192.168.11.1
iface pppoe inet manual
pre-up /sbin/ifconfig eth0 up
up ifup ppp0=dsl
down ifdown ppp0=dsl
post-down /sbin/ifconfig eth0 down
# The following is used internally only
iface dsl inet ppp
provider dsl-provider
iface pots inet ppp
provider provider</pre>
<p>Please note the <span class="strong"><strong>network configuration name</strong></span> which is the token after <span class="strong"><strong><code class="literal">iface</code></strong></span> does not use the token for the <span class="strong"><strong>network interface name</strong></span>. Also, there are no <span class="strong"><strong><code class="literal">auto</code></strong></span> stanza nor <span class="strong"><strong><code class="literal">allow-hotplug</code></strong></span> stanza to start the network interface <code class="literal">eth0</code> automatically upon events.</p>
<p>Now you are ready to switch the network configuration.</p>
<p>Let's move your PC to a LAN served by the DHCP. You bring up the <span class="strong"><strong>network interface</strong></span> (the physical interface) <code class="literal">eth0</code> by assigning the <span class="strong"><strong>network configuration</strong></span> name (the logical interface name) <code class="literal">config1</code> to it by the following.</p>
<pre class="screen">$ sudo ifup eth0=config1
Password:
...</pre>
<p>The interface <code class="literal">eth0</code> is up, configured by DHCP and connected to LAN.</p>
<pre class="screen">$ sudo ifdown eth0=config1
...</pre>
<p>The interface <code class="literal">eth0</code> is down and disconnected from LAN.</p>
<p>Let's move your PC to a LAN served by the static IP. You bring up the <span class="strong"><strong>network interface</strong></span> <code class="literal">eth0</code> by assigning the <span class="strong"><strong>network configuration</strong></span> name <code class="literal">config2</code> to it by the following.</p>
<pre class="screen">$ sudo ifup eth0=config2
...</pre>
<p>The interface <code class="literal">eth0</code> is up, configured with static IP and connected to LAN. The additional parameters given as <code class="literal">dns-*</code> configures "<code class="literal">/etc/resolv.conf</code>" contents. This "<code class="literal">/etc/resolv.conf</code>" is better manged if the <code class="literal">resolvconf</code> package is installed.</p>
<pre class="screen">$ sudo ifdown eth0=config2
...</pre>
<p>The interface <code class="literal">eth0</code> is down and disconnected from LAN, again.</p>
<p>Let's move your PC to a port on BB-modem connected to the PPPoE served service. You bring up the <span class="strong"><strong>network interface</strong></span> <code class="literal">eth0</code> by assigning the <span class="strong"><strong>network configuration</strong></span> name <code class="literal">pppoe</code> to it by the following.</p>
<pre class="screen">$ sudo ifup eth0=pppoe
...</pre>
<p>The interface <code class="literal">eth0</code> is up, configured with PPPoE connection directly to the ISP.</p>
<pre class="screen">$ sudo ifdown eth0=pppoe
...</pre>
<p>The interface <code class="literal">eth0</code> is down and disconnected, again.</p>
<p>Let's move your PC to a location without LAN or BB-modem but with POTS and modem. You bring up the <span class="strong"><strong>network interface</strong></span> <code class="literal">ppp0</code> by assigning the <span class="strong"><strong>network configuration</strong></span> name <code class="literal">pots</code> to it by the following.</p>
<pre class="screen">$ sudo ifup ppp0=pots
...</pre>
<p>The interface <code class="literal">ppp0</code> is up and connected to the Internet with PPP.</p>
<pre class="screen">$ sudo ifdown ppp0=pots
...</pre>
<p>The interface <code class="literal">ppp0</code> is down and disconnected from the Internet.</p>
<p>You should check the "<code class="literal">/etc/network/run/ifstate</code>" file for the current network configuration state of the <code class="literal">ifupdown</code> system.</p>
<div class="warning" style="margin-left: 0.5in; margin-right: 0.5in;">
<table border="0" summary="Warning">
<tr>
<td rowspan="2" align="center" valign="top">
<img alt="[Warning]" src="images/warning.png"/>
</td>
<th align="left">Warning</th>
</tr>
<tr>
<td align="left" valign="top">
<p>You may need to adjust numbers at the end of <code class="literal">eth*</code>, <code class="literal">ppp*</code>, etc. if you have multiple network interfaces.</p>
</td>
</tr>
</table>
</div>
</div>
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="_scripting_with_the_ifupdown_system"/>5.6.7. Scripting with the ifupdown system</h3>
</div>
</div>
</div>
<p>The <code class="literal">ifupdown</code> system automatically runs scripts installed in "<code class="literal">/etc/network/*/</code>" while exporting environment variables to scripts.</p>
<div class="table">
<a id="listofenvironmenheifupdownsystem"/>
<p class="title">
<strong>Table 5.14. List of environment variables passed by the ifupdown system</strong>
</p>
<div class="table-contents">
<table class="table" summary="List of environment variables passed by the ifupdown system" border="1">
<colgroup>
<col style="text-align: left"/>
<col style="text-align: left"/>
</colgroup>
<thead>
<tr>
<th style="text-align: left">
environment variable
</th>
<th style="text-align: left">
value passed
</th>
</tr>
</thead>
<tbody>
<tr>
<td style="text-align: left">
"<code class="literal">$IFACE</code>"
</td>
<td style="text-align: left">
physical name (interface name) of the interface being processed
</td>
</tr>
<tr>
<td style="text-align: left">
"<code class="literal">$LOGICAL</code>"
</td>
<td style="text-align: left">
logical name (configuration name) of the interface being processed
</td>
</tr>
<tr>
<td style="text-align: left">
"<code class="literal">$ADDRFAM</code>"
</td>
<td style="text-align: left">
<address_family> of the interface
</td>
</tr>
<tr>
<td style="text-align: left">
"<code class="literal">$METHOD</code>"
</td>
<td style="text-align: left">
<method_name> of the interface (e.g., "static")
</td>
</tr>
<tr>
<td style="text-align: left">
"<code class="literal">$MODE</code>"
</td>
<td style="text-align: left">
"start" if run from <code class="literal">ifup</code>, "stop" if run from <code class="literal">ifdown</code>
</td>
</tr>
<tr>
<td style="text-align: left">
"<code class="literal">$PHASE</code>"
</td>
<td style="text-align: left">
as per "<code class="literal">$MODE</code>", but with finer granularity, distinguishing the <code class="literal">pre-up</code>, <code class="literal">post-up</code>, <code class="literal">pre-down</code> and <code class="literal">post-down</code> phases
</td>
</tr>
<tr>
<td style="text-align: left">
"<code class="literal">$VERBOSITY</code>"
</td>
<td style="text-align: left">
indicates whether "<code class="literal">--verbose</code>" was used; set to 1 if so, 0 if not
</td>
</tr>
<tr>
<td style="text-align: left">
"<code class="literal">$PATH</code>"
</td>
<td style="text-align: left">
command search path: "<code class="literal">/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin</code>"
</td>
</tr>
<tr>
<td style="text-align: left">
"<code class="literal">$IF_<OPTION></code>"
</td>
<td style="text-align: left">
value for the corresponding option under the <span class="strong"><strong><code class="literal">iface</code></strong></span> stanza
</td>
</tr>
</tbody>
</table>
</div>
</div>
<br class="table-break"/>
<p>Here, each environment variable, "<code class="literal">$IF_<OPTION></code>", is created from the name for the corresponding option such as <option1> and <option2> by prepending "<code class="literal">$IF_</code>", converting the case to the upper case, replacing hyphens to underscores, and discarding non-alphanumeric characters.</p>
<div class="tip" style="margin-left: 0.5in; margin-right: 0.5in;">
<table border="0" summary="Tip">
<tr>
<td rowspan="2" align="center" valign="top">
<img alt="[Tip]" src="images/tip.png"/>
</td>
<th align="left">Tip</th>
</tr>
<tr>
<td align="left" valign="top">
<p>See <a class="xref" href="ch05.en.html#_the_basic_syntax_of_etc_network_interfaces" title="5.5.2. The basic syntax of "/etc/network/interfaces"">Section 5.5.2, “The basic syntax of "/etc/network/interfaces"”</a> for <address_family>, <method_name>, <option1> and <option2>.</p>
</td>
</tr>
</table>
</div>
<p>The <code class="literal">ifupdown-extra</code> package (see <a class="xref" href="ch05.en.html#_the_ifupdown_extra_package" title="5.5.14. The ifupdown-extra package">Section 5.5.14, “The ifupdown-extra package”</a>) uses these environment variables to extend the functionality of the <code class="literal">ifupdown</code> package. The <code class="literal">ifmetric</code> package (see <a class="xref" href="ch05.en.html#_the_ifmetric_package" title="5.6.2. The ifmetric package">Section 5.6.2, “The ifmetric package”</a>) installs the "<code class="literal">/etc/network/if-up.d/ifmetric</code>" script which sets the metric via the "<code class="literal">$IF_METRIC</code>" variable. The <code class="literal">guessnet</code> package (see <a class="xref" href="ch05.en.html#_mapping_with_guessnet" title="5.6.8. Mapping with guessnet">Section 5.6.8, “Mapping with guessnet”</a>), which provides simple and powerful framework for the auto-selection of the network configuration via the mapping mechanism, also uses these.</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<table border="0" summary="Note">
<tr>
<td rowspan="2" align="center" valign="top">
<img alt="[Note]" src="images/note.png"/>
</td>
<th align="left">Note</th>
</tr>
<tr>
<td align="left" valign="top">
<p>For more specific examples of custom network configuration scripts using these environment variables, you should check example scripts in "<code class="literal">/usr/share/doc/ifupdown/examples/*</code>" and scripts used in <code class="literal">ifscheme</code> and <code class="literal">ifupdown-scripts-zg2</code> packages. These additional scripts have some overlaps of functionalities with basic <code class="literal">ifupdown-extra</code> and <code class="literal">guessnet</code> packages. If you install these additional scripts, you should customize these scripts to avoid interferences.</p>
</td>
</tr>
</table>
</div>
</div>
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="_mapping_with_guessnet"/>5.6.8. Mapping with guessnet</h3>
</div>
</div>
</div>
<p>Instead of manually choosing configuration as described in <a class="xref" href="ch05.en.html#_the_manually_switchable_network_configuration" title="5.6.6. The manually switchable network configuration">Section 5.6.6, “The manually switchable network configuration”</a>, you can use the mapping mechanism described in <a class="xref" href="ch05.en.html#_the_mapping_stanza" title="5.6.5. The mapping stanza">Section 5.6.5, “The mapping stanza”</a> to select network configuration automatically with custom scripts.</p>
<p>The <span class="citerefentry"><span class="refentrytitle">guessnet-ifupdown</span>(8)</span> command provided by the <code class="literal">guessnet</code> package is designed to be used as a mapping script and provides powerful framework to enhance the <code class="literal">ifupdown</code> system.</p>
<div class="itemizedlist">
<ul class="itemizedlist">
<li class="listitem">
<p>
You list test condition as the value for <span class="strong"><strong><code class="literal">guessnet</code></strong></span> options for each network configuration under <span class="strong"><strong><code class="literal">iface</code></strong></span> stanza.
</p>
</li>
<li class="listitem">
<p>
Mapping choses the <span class="strong"><strong><code class="literal">iface</code></strong></span> with first non-ERROR result as the network configuration.
</p>
</li>
</ul>
</div>
<p>This dual usage of the "<code class="literal">/etc/network/interfaces</code>" file by the mapping script, <code class="literal">guessnet-ifupdown</code>, and the original network configuration infrastructure, <code class="literal">ifupdown</code>, does not cause negative impacts since <span class="strong"><strong><code class="literal">guessnet</code></strong></span> options only export extra environment variables to scripts run by the <code class="literal">ifupdown</code> system. See details in <span class="citerefentry"><span class="refentrytitle">guessnet-ifupdown</span>(8)</span>.</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<table border="0" summary="Note">
<tr>
<td rowspan="2" align="center" valign="top">
<img alt="[Note]" src="images/note.png"/>
</td>
<th align="left">Note</th>
</tr>
<tr>
<td align="left" valign="top">
<p>When multiple <span class="strong"><strong><code class="literal">guessnet</code></strong></span> option lines are required in "<code class="literal">/etc/network/interfaces</code>", use option lines started with <span class="strong"><strong><code class="literal">guessnet1</code></strong></span>, <span class="strong"><strong><code class="literal">guessnet2</code></strong></span>, and so on, since the <code class="literal">ifupdown</code> package does not allow starting strings of option lines to be repeated.</p>
</td>
</tr>
</table>
</div>
</div>
</div>
<div class="section">
<div class="titlepage">
<div>
<div>
<h2 class="title"><a id="_the_low_level_network_configuration"/>5.7. The low level network configuration</h2>
</div>
</div>
</div>
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="_iproute2_commands"/>5.7.1. Iproute2 commands</h3>
</div>
</div>
</div>
<p><a class="ulink" href="http://www.linuxfoundation.org/collaborate/workgroups/networking/iproute2">Iproute2</a> commands offer complete low-level network configuration capabilities. Here is a translation table from obsolete <a class="ulink" href="http://www.linuxfoundation.org/collaborate/workgroups/networking/net-tools">net-tools</a> commands to new <a class="ulink" href="http://www.linuxfoundation.org/collaborate/workgroups/networking/iproute2">iproute2</a> etc. commands.</p>
<div class="table">
<a id="translationtableiprouteccommands"/>
<p class="title">
<strong>Table 5.15. Translation table from obsolete <code class="literal">net-tools</code> commands to new <code class="literal">iproute2</code> commands</strong>
</p>
<div class="table-contents">
<table class="table" summary="Translation table from obsolete net-tools commands to new iproute2 commands" border="1">
<colgroup>
<col style="text-align: left"/>
<col style="text-align: left"/>
<col style="text-align: left"/>
</colgroup>
<thead>
<tr>
<th style="text-align: left">
obsolete net-tools
</th>
<th style="text-align: left">
new iproute2 etc.
</th>
<th style="text-align: left">
manipulation
</th>
</tr>
</thead>
<tbody>
<tr>
<td style="text-align: left"><span class="citerefentry"><span class="refentrytitle">ifconfig</span>(8)</span>
</td>
<td style="text-align: left">
<code class="literal">ip addr</code>
</td>
<td style="text-align: left">
protocol (IP or IPv6) address on a device
</td>
</tr>
<tr>
<td style="text-align: left"><span class="citerefentry"><span class="refentrytitle">route</span>(8)</span>
</td>
<td style="text-align: left">
<code class="literal">ip route</code>
</td>
<td style="text-align: left">
routing table entry
</td>
</tr>
<tr>
<td style="text-align: left"><span class="citerefentry"><span class="refentrytitle">arp</span>(8)</span>
</td>
<td style="text-align: left">
<code class="literal">ip neigh</code>
</td>
<td style="text-align: left">
ARP or NDISC cache entry
</td>
</tr>
<tr>
<td style="text-align: left">
<code class="literal">ipmaddr</code>
</td>
<td style="text-align: left">
<code class="literal">ip maddr</code>
</td>
<td style="text-align: left">
multicast address
</td>
</tr>
<tr>
<td style="text-align: left">
<code class="literal">iptunnel</code>
</td>
<td style="text-align: left">
<code class="literal">ip tunnel</code>
</td>
<td style="text-align: left">
tunnel over IP
</td>
</tr>
<tr>
<td style="text-align: left"><span class="citerefentry"><span class="refentrytitle">nameif</span>(8)</span>
</td>
<td style="text-align: left"><span class="citerefentry"><span class="refentrytitle">ifrename</span>(8)</span>
</td>
<td style="text-align: left">
name network interfaces based on MAC addresses
</td>
</tr>
<tr>
<td style="text-align: left"><span class="citerefentry"><span class="refentrytitle">mii-tool</span>(8)</span>
</td>
<td style="text-align: left"><span class="citerefentry"><span class="refentrytitle">ethtool</span>(8)</span>
</td>
<td style="text-align: left">
Ethernet device settings
</td>
</tr>
</tbody>
</table>
</div>
</div>
<br class="table-break"/>
<p>See <span class="citerefentry"><span class="refentrytitle">ip</span>(8)</span> and <a class="ulink" href="http://www.policyrouting.org/iproute2.doc.html">IPROUTE2 Utility Suite Howto</a>.</p>
</div>
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="_safe_low_level_network_operations"/>5.7.2. Safe low level network operations</h3>
</div>
</div>
</div>
<p>You may use low level network commands as follows safely since they do not change network configuration.</p>
<div class="table">
<a id="listoflowlevelnetworkcommands"/>
<p class="title">
<strong>Table 5.16. List of low level network commands</strong>
</p>
<div class="table-contents">
<table class="table" summary="List of low level network commands" border="1">
<colgroup>
<col style="text-align: left"/>
<col style="text-align: left"/>
</colgroup>
<thead>
<tr>
<th style="text-align: left">
command
</th>
<th style="text-align: left">
description
</th>
</tr>
</thead>
<tbody>
<tr>
<td style="text-align: left">
<code class="literal">ifconfig</code>
</td>
<td style="text-align: left">
display the link and address status of active interfaces
</td>
</tr>
<tr>
<td style="text-align: left">
<code class="literal">ip addr show</code>
</td>
<td style="text-align: left">
display the link and address status of active interfaces
</td>
</tr>
<tr>
<td style="text-align: left">
<code class="literal">route -n</code>
</td>
<td style="text-align: left">
display all the routing table in numerical addresses
</td>
</tr>
<tr>
<td style="text-align: left">
<code class="literal">ip route show</code>
</td>
<td style="text-align: left">
display all the routing table in numerical addresses
</td>
</tr>
<tr>
<td style="text-align: left">
<code class="literal">arp</code>
</td>
<td style="text-align: left">
display the current content of the <a class="ulink" href="http://en.wikipedia.org/wiki/Address_Resolution_Protocol">ARP</a> cache tables
</td>
</tr>
<tr>
<td style="text-align: left">
<code class="literal">ip neigh</code>
</td>
<td style="text-align: left">
display the current content of the <a class="ulink" href="http://en.wikipedia.org/wiki/Address_Resolution_Protocol">ARP</a> cache tables
</td>
</tr>
<tr>
<td style="text-align: left">
<code class="literal">plog</code>
</td>
<td style="text-align: left">
display ppp daemon log
</td>
</tr>
<tr>
<td style="text-align: left">
<code class="literal">ping yahoo.com</code>
</td>
<td style="text-align: left">
check the Internet connection to "<code class="literal">yahoo.com</code>"
</td>
</tr>
<tr>
<td style="text-align: left">
<code class="literal">whois yahoo.com</code>
</td>
<td style="text-align: left">
check who registered "<code class="literal">yahoo.com</code>" in the domains database
</td>
</tr>
<tr>
<td style="text-align: left">
<code class="literal">traceroute yahoo.com</code>
</td>
<td style="text-align: left">
trace the Internet connection to "<code class="literal">yahoo.com</code>"
</td>
</tr>
<tr>
<td style="text-align: left">
<code class="literal">tracepath yahoo.com</code>
</td>
<td style="text-align: left">
trace the Internet connection to "<code class="literal">yahoo.com</code>"
</td>
</tr>
<tr>
<td style="text-align: left">
<code class="literal">mtr yahoo.com</code>
</td>
<td style="text-align: left">
trace the Internet connection to "<code class="literal">yahoo.com</code>" (repeatedly)
</td>
</tr>
<tr>
<td style="text-align: left">
<code class="literal">dig [@dns-server.com] example.com [{a|mx|any}]</code>
</td>
<td style="text-align: left">
check <a class="ulink" href="http://en.wikipedia.org/wiki/Domain_Name_System">DNS</a> records of "<code class="literal">example.com</code>" by "<code class="literal">dns-server.com</code>" for a "<code class="literal">a</code>", "<code class="literal">mx</code>", or "<code class="literal">any</code>" record
</td>
</tr>
<tr>
<td style="text-align: left">
<code class="literal">iptables -L -n</code>
</td>
<td style="text-align: left">
check packet filter
</td>
</tr>
<tr>
<td style="text-align: left">
<code class="literal">netstat -a</code>
</td>
<td style="text-align: left">
find all open ports
</td>
</tr>
<tr>
<td style="text-align: left">
<code class="literal">netstat -l --inet</code>
</td>
<td style="text-align: left">
find listening ports
</td>
</tr>
<tr>
<td style="text-align: left">
<code class="literal">netstat -ln --tcp</code>
</td>
<td style="text-align: left">
find listening TCP ports (numeric)
</td>
</tr>
<tr>
<td style="text-align: left">
<code class="literal">dlint example.com</code>
</td>
<td style="text-align: left">
check DNS zone information of "<code class="literal">example.com</code>"
</td>
</tr>
</tbody>
</table>
</div>
</div>
<br class="table-break"/>
<div class="tip" style="margin-left: 0.5in; margin-right: 0.5in;">
<table border="0" summary="Tip">
<tr>
<td rowspan="2" align="center" valign="top">
<img alt="[Tip]" src="images/tip.png"/>
</td>
<th align="left">Tip</th>
</tr>
<tr>
<td align="left" valign="top">
<p>Some of these low level network configuration tools reside in "<code class="literal">/sbin/</code>". You may need to issue full command path such as "<code class="literal">/sbin/ifconfig</code>" or add "<code class="literal">/sbin</code>" to the "<code class="literal">$PATH</code>" list in your "<code class="literal">~/.bashrc</code>".</p>
</td>
</tr>
</table>
</div>
</div>
</div>
<div class="section">
<div class="titlepage">
<div>
<div>
<h2 class="title"><a id="_network_optimization"/>5.8. Network optimization</h2>
</div>
</div>
</div>
<p>Generic network optimization is beyond the scope of this documentation. I touch only subjects pertinent to the consumer grade connection.</p>
<div class="table">
<a id="listofnetworkoptimizationtools"/>
<p class="title">
<strong>Table 5.17. List of network optimization tools</strong>
</p>
<div class="table-contents">
<table class="table" summary="List of network optimization tools" border="1">
<colgroup>
<col style="text-align: left"/>
<col style="text-align: left"/>
<col style="text-align: left"/>
<col style="text-align: left"/>
</colgroup>
<thead>
<tr>
<th style="text-align: left">
packages
</th>
<th style="text-align: left">
popcon
</th>
<th style="text-align: left">
size
</th>
<th style="text-align: left">
description
</th>
</tr>
</thead>
<tbody>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/iftop">
<code class="literal">iftop</code>
</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=iftop">V:9, I:111</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/i/iftop.html">93</a>
</td>
<td style="text-align: left">
display bandwidth usage information on an network interface
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/iperf">
<code class="literal">iperf</code>
</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=iperf">V:4, I:54</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/i/iperf.html">160</a>
</td>
<td style="text-align: left">
Internet Protocol bandwidth measuring tool
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/apt-spy">
<code class="literal">apt-spy</code>
</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=apt-spy">V:0, I:3</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/a/apt-spy.html">105</a>
</td>
<td style="text-align: left">
write a "<code class="literal">/etc/apt/sources.list</code>" file based on bandwidth tests
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/ifstat">
<code class="literal">ifstat</code>
</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=ifstat">V:1, I:10</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/i/ifstat.html">55</a>
</td>
<td style="text-align: left">
InterFace STATistics Monitoring
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/bmon">
<code class="literal">bmon</code>
</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=bmon">V:1, I:12</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/b/bmon.html">139</a>
</td>
<td style="text-align: left">
portable bandwidth monitor and rate estimator
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/ethstatus">
<code class="literal">ethstatus</code>
</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=ethstatus">V:0, I:4</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/e/ethstatus.html">39</a>
</td>
<td style="text-align: left">
script that quickly measures network device throughput
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/bing">
<code class="literal">bing</code>
</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=bing">V:0, I:2</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/b/bing.html">62</a>
</td>
<td style="text-align: left">
empirical stochastic bandwidth tester
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/bwm-ng">
<code class="literal">bwm-ng</code>
</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=bwm-ng">V:2, I:17</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/b/bwm-ng.html">88</a>
</td>
<td style="text-align: left">
small and simple console-based bandwidth monitor
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/ethstats">
<code class="literal">ethstats</code>
</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=ethstats">V:0, I:1</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/e/ethstats.html">20</a>
</td>
<td style="text-align: left">
console-based Ethernet statistics monitor
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/ipfm">
<code class="literal">ipfm</code>
</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=ipfm">V:0, I:0</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/i/ipfm.html">78</a>
</td>
<td style="text-align: left">
bandwidth analysis tool
</td>
</tr>
</tbody>
</table>
</div>
</div>
<br class="table-break"/>
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="_finding_optimal_mtu"/>5.8.1. Finding optimal MTU</h3>
</div>
</div>
</div>
<p>The <a class="ulink" href="http://en.wikipedia.org/wiki/Maximum_transmission_unit">Maximum Transmission Unit (MTU)</a> value can be determined experimentally with <span class="citerefentry"><span class="refentrytitle">ping</span>(8)</span> with "<code class="literal">-M do</code>" option which sends ICMP packets with data size starting from 1500 (with offset of 28 bytes for the IP+ICMP header) and finding the largest size without IP fragmentation.</p>
<p>For example, try the following</p>
<pre class="screen">$ ping -c 1 -s $((1500-28)) -M do www.debian.org
PING www.debian.org (194.109.137.218) 1472(1500) bytes of data.
From 192.168.11.2 icmp_seq=1 Frag needed and DF set (mtu = 1454)
--- www.debian.org ping statistics ---
0 packets transmitted, 0 received, +1 errors</pre>
<p>Try 1454 instead of 1500</p>
<p>You see <span class="citerefentry"><span class="refentrytitle">ping</span>(8)</span> succeed with 1454.</p>
<p>This process is <a class="ulink" href="http://en.wikipedia.org/wiki/Path_MTU_discovery">Path MTU (PMTU) discovery</a> (<a class="ulink" href="http://tools.ietf.org/html/rfc1191">RFC1191</a>) and the <span class="citerefentry"><span class="refentrytitle">tracepath</span>(8)</span> command can automate this.</p>
<div class="tip" style="margin-left: 0.5in; margin-right: 0.5in;">
<table border="0" summary="Tip">
<tr>
<td rowspan="2" align="center" valign="top">
<img alt="[Tip]" src="images/tip.png"/>
</td>
<th align="left">Tip</th>
</tr>
<tr>
<td align="left" valign="top">
<p>The above example with PMTU value of 1454 is for my previous FTTP provider which used <a class="ulink" href="http://en.wikipedia.org/wiki/Asynchronous_Transfer_Mode">Asynchronous Transfer Mode</a> (ATM) as its backbone network and served its clients with the <a class="ulink" href="http://en.wikipedia.org/wiki/Point-to-Point_Protocol_over_Ethernet">PPPoE</a>. The actual PMTU value depends on your environment, e.g., 1500 for the my new FTTP provider.</p>
</td>
</tr>
</table>
</div>
<div class="table">
<a id="basicguidelinesoeoptimalmtuvalue"/>
<p class="title">
<strong>Table 5.18. Basic guide lines of the optimal MTU value</strong>
</p>
<div class="table-contents">
<table class="table" summary="Basic guide lines of the optimal MTU value" border="1">
<colgroup>
<col style="text-align: left"/>
<col style="text-align: left"/>
<col style="text-align: left"/>
</colgroup>
<thead>
<tr>
<th style="text-align: left">
network environment
</th>
<th style="text-align: left">
MTU
</th>
<th style="text-align: left">
rationale
</th>
</tr>
</thead>
<tbody>
<tr>
<td style="text-align: left">
Dial-up link (IP: PPP)
</td>
<td style="text-align: left">
576
</td>
<td style="text-align: left">
standard
</td>
</tr>
<tr>
<td style="text-align: left">
Ethernet link (IP: DHCP or fixed)
</td>
<td style="text-align: left">
1500
</td>
<td style="text-align: left">
standard and default
</td>
</tr>
<tr>
<td style="text-align: left">
Ethernet link (IP: PPPoE)
</td>
<td style="text-align: left">
1492 (=1500-8)
</td>
<td style="text-align: left">
2 bytes for PPP header and 6 bytes for PPPoE header
</td>
</tr>
<tr>
<td style="text-align: left">
Ethernet link (ISP's backbone: ATM, IP: DHCP or fixed)
</td>
<td style="text-align: left">
1462 (=48*31-18-8)
</td>
<td style="text-align: left">
author's speculation: 18 bytes for Ethernet header, 8 bytes for SAR trailer
</td>
</tr>
<tr>
<td style="text-align: left">
Ethernet link (ISP's backbone: ATM, IP: PPPoE)
</td>
<td style="text-align: left">
1454 (=48*31-8-18-8)
</td>
<td style="text-align: left">
see "<a class="ulink" href="http://www.mynetwatchman.com/kb/ADSL/pppoemtu.htm">Optimal MTU configuration for PPPoE ADSL Connections</a>" for rationale
</td>
</tr>
</tbody>
</table>
</div>
</div>
<br class="table-break"/>
<p>In addtion to these basic guide lines, you should know the following.</p>
<div class="itemizedlist">
<ul class="itemizedlist">
<li class="listitem">
<p>
Any use of tunneling methods (<a class="ulink" href="http://en.wikipedia.org/wiki/Virtual_private_network">VPN</a> etc.) may reduce optimal MTU further by their overheads.
</p>
</li>
<li class="listitem">
<p>
The MTU value should not exceed the experimentally determined PMTU value.
</p>
</li>
<li class="listitem">
<p>
The bigger MTU value is generally better when other limitations are met.
</p>
</li>
</ul>
</div>
</div>
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="_setting_mtu"/>5.8.2. Setting MTU</h3>
</div>
</div>
</div>
<p>Here are examples for setting the MTU value from its default 1500 to 1454.</p>
<p>For the DHCP (see <a class="xref" href="ch05.en.html#_the_network_interface_served_by_the_dhcp" title="5.5.4. The network interface served by the DHCP">Section 5.5.4, “The network interface served by the DHCP”</a>), you can replace pertinent <span class="strong"><strong><code class="literal">iface</code></strong></span> stanza lines in the "<code class="literal">/etc/network/interfaces</code>" with the following.</p>
<pre class="screen">iface eth0 inet dhcp
pre-up /sbin/ifconfig $IFACE mtu 1454</pre>
<p>For the static IP (see <a class="xref" href="ch05.en.html#_the_network_interface_with_the_static_ip" title="5.5.5. The network interface with the static IP">Section 5.5.5, “The network interface with the static IP”</a>), you can replace pertinent <span class="strong"><strong><code class="literal">iface</code></strong></span> stanza lines in the "<code class="literal">/etc/network/interfaces</code>" with the following.</p>
<pre class="screen">iface eth0 inet static
address 192.168.11.100
netmask 255.255.255.0
gateway 192.168.11.1
mtu 1454
dns-domain example.com
dns-nameservers 192.168.11.1</pre>
<p>For the direct PPPoE (see <a class="xref" href="ch05.en.html#_the_pppoe_connection_with_pppoeconf" title="5.4.5. The PPPoE connection with pppoeconf">Section 5.4.5, “The PPPoE connection with pppoeconf”</a>), you can replace pertinent "<code class="literal">mtu</code>" line in the "<code class="literal">/etc/ppp/peers/dsl-provider</code>" with the following.</p>
<pre class="screen">mtu 1454</pre>
<p>The <a class="ulink" href="http://en.wikipedia.org/wiki/Maximum_segment_size">maximum segment size</a> (MSS) is used as an alternative measure of packet size. The relationship between MSS and MTU are the following.</p>
<div class="itemizedlist">
<ul class="itemizedlist">
<li class="listitem">
<p>
MSS = MTU - 40 for IPv4
</p>
</li>
<li class="listitem">
<p>
MSS = MTU - 60 for IPv6
</p>
</li>
</ul>
</div>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<table border="0" summary="Note">
<tr>
<td rowspan="2" align="center" valign="top">
<img alt="[Note]" src="images/note.png"/>
</td>
<th align="left">Note</th>
</tr>
<tr>
<td align="left" valign="top">
<p>The <span class="citerefentry"><span class="refentrytitle">iptables</span>(8)</span> (see <a class="xref" href="ch05.en.html#_netfilter_infrastructure" title="5.9. Netfilter infrastructure">Section 5.9, “Netfilter infrastructure”</a>) based optimization can clamp packet size by the MSS and is useful for the router. See "TCPMSS" in <span class="citerefentry"><span class="refentrytitle">iptables</span>(8)</span>.</p>
</td>
</tr>
</table>
</div>
</div>
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="_wan_tcp_optimization"/>5.8.3. WAN TCP optimization</h3>
</div>
</div>
</div>
<p>The TCP throughput can be maximized by adjusting TCP buffer size parameters as described in "<a class="ulink" href="http://dsd.lbl.gov/TCP-tuning/">TCP Tuning Guide</a>" and "<a class="ulink" href="http://en.wikipedia.org/wiki/TCP_tuning">TCP tuning</a>" for the modern high-bandwidth and high-latency WAN. So far, the current Debian default settings serve well even for my LAN connected by the fast 1G bps FTTP service.</p>
</div>
</div>
<div class="section">
<div class="titlepage">
<div>
<div>
<h2 class="title"><a id="_netfilter_infrastructure"/>5.9. Netfilter infrastructure</h2>
</div>
</div>
</div>
<p><a class="ulink" href="http://en.wikipedia.org/wiki/Netfilter">Netfilter</a> provides infrastructure for <a class="ulink" href="http://en.wikipedia.org/wiki/Stateful_firewall">stateful firewall</a> and <a class="ulink" href="http://en.wikipedia.org/wiki/Network_address_translation">network address translation (NAT)</a> with <a class="ulink" href="http://en.wikipedia.org/wiki/Linux_kernel">Linux kernel</a> modules (see <a class="xref" href="ch03.en.html#_the_kernel_module_initialization" title="3.3.1. The kernel module initialization">Section 3.3.1, “The kernel module initialization”</a>).</p>
<div class="table">
<a id="listoffirewalltools"/>
<p class="title">
<strong>Table 5.19. List of firewall tools</strong>
</p>
<div class="table-contents">
<table class="table" summary="List of firewall tools" border="1">
<colgroup>
<col style="text-align: left"/>
<col style="text-align: left"/>
<col style="text-align: left"/>
<col style="text-align: left"/>
</colgroup>
<thead>
<tr>
<th style="text-align: left">
packages
</th>
<th style="text-align: left">
popcon
</th>
<th style="text-align: left">
size
</th>
<th style="text-align: left">
description
</th>
</tr>
</thead>
<tbody>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/iptables">
<code class="literal">iptables</code>
</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=iptables">V:240, I:993</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/i/iptables.html">1528</a>
</td>
<td style="text-align: left">
administration tools for <a class="ulink" href="http://en.wikipedia.org/wiki/Netfilter">netfilter</a> (<span class="citerefentry"><span class="refentrytitle">iptables</span>(8)</span> for IPv4, <span class="citerefentry"><span class="refentrytitle">ip6tables</span>(8)</span> for IPv6)
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/arptables">
<code class="literal">arptables</code>
</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=arptables">V:0, I:2</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/a/arptables.html">84</a>
</td>
<td style="text-align: left">
administration tools for <a class="ulink" href="http://en.wikipedia.org/wiki/Netfilter">netfilter</a> (<span class="citerefentry"><span class="refentrytitle">arptables</span>(8)</span> for ARP)
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/ebtables">
<code class="literal">ebtables</code>
</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=ebtables">V:30, I:56</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/e/ebtables.html">351</a>
</td>
<td style="text-align: left">
administration tools for <a class="ulink" href="http://en.wikipedia.org/wiki/Netfilter">netfilter</a> (<span class="citerefentry"><span class="refentrytitle">ebtables</span>(8)</span> for Ethernet bridging)
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/iptstate">
<code class="literal">iptstate</code>
</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=iptstate">V:0, I:4</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/i/iptstate.html">116</a>
</td>
<td style="text-align: left">
continuously monitor <a class="ulink" href="http://en.wikipedia.org/wiki/Netfilter">netfilter</a> state (similar to <span class="citerefentry"><span class="refentrytitle">top</span>(1)</span>)
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/shorewall-init">
<code class="literal">shorewall-init</code>
</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=shorewall-init">V:0, I:0</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/s/shorewall-init.html">80</a>
</td>
<td style="text-align: left"><a class="ulink" href="http://en.wikipedia.org/wiki/Shorewall">Shoreline Firewall</a> initialization
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/shorewall">
<code class="literal">shorewall</code>
</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=shorewall">V:6, I:16</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/s/shorewall.html">2343</a>
</td>
<td style="text-align: left"><a class="ulink" href="http://en.wikipedia.org/wiki/Shorewall">Shoreline Firewall</a>, <a class="ulink" href="http://en.wikipedia.org/wiki/Netfilter">netfilter</a> configuration file generator
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/shorewall-lite">
<code class="literal">shorewall-lite</code>
</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=shorewall-lite">V:0, I:0</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/s/shorewall-lite.html">85</a>
</td>
<td style="text-align: left"><a class="ulink" href="http://en.wikipedia.org/wiki/Shorewall">Shoreline Firewall</a>, <a class="ulink" href="http://en.wikipedia.org/wiki/Netfilter">netfilter</a> configuration file generator (light version)
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/shorewall6">
<code class="literal">shorewall6</code>
</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=shorewall6">V:0, I:2</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/s/shorewall6.html">895</a>
</td>
<td style="text-align: left"><a class="ulink" href="http://en.wikipedia.org/wiki/Shorewall">Shoreline Firewall</a>, <a class="ulink" href="http://en.wikipedia.org/wiki/Netfilter">netfilter</a> configuration file generator (IPv6 version)
</td>
</tr>
<tr>
<td style="text-align: left">
<a class="ulink" href="http://packages.debian.org/sid/shorewall6-lite">
<code class="literal">shorewall6-lite</code>
</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://qa.debian.org/popcon.php?package=shorewall6-lite">V:0, I:0</a>
</td>
<td style="text-align: left">
<a class="ulink" href="http://packages.qa.debian.org/s/shorewall6-lite.html">83</a>
</td>
<td style="text-align: left"><a class="ulink" href="http://en.wikipedia.org/wiki/Shorewall">Shoreline Firewall</a>, <a class="ulink" href="http://en.wikipedia.org/wiki/Netfilter">netfilter</a> configuration file generator (IPv6, light version)
</td>
</tr>
</tbody>
</table>
</div>
</div>
<br class="table-break"/>
<p>Main user space program of <a class="ulink" href="http://en.wikipedia.org/wiki/Netfilter">netfilter</a> is <span class="citerefentry"><span class="refentrytitle">iptables</span>(8)</span>. You can manually configure <a class="ulink" href="http://en.wikipedia.org/wiki/Netfilter">netfilter</a> interactively from shell, save its state with <span class="citerefentry"><span class="refentrytitle">iptables-save</span>(8)</span>, and restore it via init script with <span class="citerefentry"><span class="refentrytitle">iptables-restore</span>(8)</span> upon system reboot.</p>
<p>Configuration helper scripts such as <a class="ulink" href="http://en.wikipedia.org/wiki/Shorewall">shorewall</a> ease this process.</p>
<p>See documentations at <a class="ulink" href="http://www.netfilter.org/documentation/">http://www.netfilter.org/documentation/</a> (or in "<code class="literal">/usr/share/doc/iptables/html/</code>").</p>
<div class="itemizedlist">
<ul class="itemizedlist">
<li class="listitem">
<p>
<a class="ulink" href="http://www.netfilter.org/documentation/HOWTO/networking-concepts-HOWTO.html">Linux Networking-concepts HOWTO</a>
</p>
</li>
<li class="listitem">
<p>
<a class="ulink" href="http://www.netfilter.org/documentation/HOWTO/packet-filtering-HOWTO.html">Linux 2.4 Packet Filtering HOWTO</a>
</p>
</li>
<li class="listitem">
<p>
<a class="ulink" href="http://www.netfilter.org/documentation/HOWTO/NAT-HOWTO.html">Linux 2.4 NAT HOWTO</a>
</p>
</li>
</ul>
</div>
<div class="tip" style="margin-left: 0.5in; margin-right: 0.5in;">
<table border="0" summary="Tip">
<tr>
<td rowspan="2" align="center" valign="top">
<img alt="[Tip]" src="images/tip.png"/>
</td>
<th align="left">Tip</th>
</tr>
<tr>
<td align="left" valign="top">
<p>Although these were written for Linux <span class="strong"><strong>2.4</strong></span>, both <span class="citerefentry"><span class="refentrytitle">iptables</span>(8)</span> command and netfilter kernel function apply for Linux <span class="strong"><strong>2.6</strong></span> and <span class="strong"><strong>3.x</strong></span> kernel series.</p>
</td>
</tr>
</table>
</div>
</div>
</div>
<div class="navfooter">
<hr/>
<table width="100%" summary="Navigation footer">
<tr>
<td align="left"><a accesskey="p" href="ch04.en.html"><img src="images/prev.png" alt="Prev"/></a> </td>
<td align="center"> </td>
<td align="right"> <a accesskey="n" href="ch06.en.html"><img src="images/next.png" alt="Next"/></a></td>
</tr>
<tr>
<td align="left" valign="top">Chapter 4. Authentication </td>
<td align="center">
<a accesskey="h" href="index.en.html">
<img src="images/home.png" alt="Home"/>
</a>
</td>
<td align="right" valign="top"> Chapter 6. Network applications</td>
</tr>
</table>
</div>
</body>
</html>
|