1.\" $NetBSD: networks.5,v 1.7 1998/07/16 08:43:25 fair Exp $ 2.\" 3.\" Copyright (c) 1983, 1991, 1993 4.\" The Regents of the University of California. All rights reserved. 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 3. All advertising materials mentioning features or use of this software 15.\" must display the following acknowledgement: 16.\" This product includes software developed by the University of 17.\" California, Berkeley and its contributors. 18.\" 4. Neither the name of the University nor the names of its contributors 19.\" may be used to endorse or promote products derived from this software 20.\" without specific prior written permission. 21.\" 22.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32.\" SUCH DAMAGE. 33.\" 34.\" @(#)networks.5 8.1 (Berkeley) 6/5/93 35.\" 36.Dd July 4, 1998 37.Dt NETWORKS 5 38.Os BSD 4.2 39.Sh NAME 40.Nm networks 41.Nd Internet Protocol network name data base 42.Sh DESCRIPTION 43The 44.Nm 45file is used to translate between Internet Protocol 46.Pq Tn IP 47network addresses and network names (and vice versa) when 48.Xr named 8 49is either not running (e.g. at boot time), or not configured. 50.Pp 51While the 52.Nm 53file was originally intended to be an exhaustive list of all 54.Tn IP 55networks that the local host could communicate with, distribution 56and update of such a list for the world-wide 57.Tn Internet 58(or, indeed, for any large "enterprise" network) has proven to be 59prohibitive, so the Domain Name System 60.Pq Tn DNS 61is used instead, except as noted. 62.Pp 63For each 64.Tn IP 65network a single line should be present with the following information: 66.Bd -unfilled -offset indent 67official network name 68ip network number 69aliases 70.Ed 71.Pp 72Items are separated by any number of blanks and/or tab characters. 73A ``#'' indicates the beginning of a comment; characters up to the end of 74the line are not interpreted by routines which search the file. 75.Pp 76Network number may be specified in the conventional 77``.'' (dot) notation using the 78.Xr inet_network 3 79routine 80from the 81.Tn IP 82address manipulation library, 83.Xr inet 3 . 84Network names may contain 85.Qq a 86through 87.Qq z , 88zero through nine, and dash. 89.Pp 90.Tn IP 91network numbers on the 92.Tn Internet 93are generally assigned to a site by its Internet Service Provider 94.Pq Tn ISP , 95who, in turn, get network address space assigned to them by one of 96the regional Internet Registries (e.g. ARIN, RIPE NCC, APNIC). 97These registries, in turn, answer to the Internet Assigned Numbers 98Authority 99.Pq Tn IANA . 100.Pp 101If a site changes its ISP from one to another, it will generally 102be required to change all its assigned IP addresses as part of the 103conversion; that is, return the previous network numbers to the previous 104.Tn ISP , 105and assign addresses to its hosts from 106.Tn IP 107network address space given by the new 108.Tn ISP . 109Thus, it is best for a savvy network manager to configure his 110hosts for easy renumbering, to preserve his ability to easily 111change his 112.Tn ISP 113should the need arise. 114.Sh FILES 115.Bl -tag -width /etc/networks -compact 116.It Pa /etc/networks 117The 118.Nm 119file resides in 120.Pa /etc . 121.El 122.Sh SEE ALSO 123.Xr getnetent 3 , 124.Xr resolv.conf 5 , 125.Xr hostname 7 , 126.Xr dhclient 8 , 127.Xr dhcpd 8 , 128.Xr named 8 , 129.Rs 130.%R RFC 131.%N 2317 132.%D March 1998 133.%T "Classless IN-ADDR.ARPA delegation" 134.Re 135.Rs 136.%R RFC 137.%N 1918 138.%D February 1996 139.%T "Address Allocation for Private Internets" 140.Re 141.Rs 142.%R RFC 143.%N 1627 144.%D July 1994 145.%T "Network 10 Considered Harmful" 146.Re 147.Rs 148.%R RFC 149.%N 1519 150.%D September 1993 151.%T "Classless Inter-Domain Routing (CIDR): an Address Assignment and Aggregation Strategy" 152.Re 153.Rs 154.%R RFC 155.%N 1101 156.%D April 1989 157.%T "DNS Encoding of Network Names and Other Types" 158.Re 159.Sh HISTORY 160The 161.Nm 162file format appeared in 163.Bx 4.2 . 164