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NetBSD 6.1.5 - man page for networks (netbsd section 5)

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NETWORKS(5)			     BSD File Formats Manual			      NETWORKS(5)

NAME
     networks -- Internet Protocol network name data base

DESCRIPTION
     The networks file is used as a local source to translate between Internet Protocol (IP) net-
     work addresses and network names (and vice versa).  It can be used in conjunction with the
     DNS, as controlled by nsswitch.conf(5).

     While the networks file was originally intended to be an exhaustive list of all IP networks
     that the local host could communicate with, distribution and update of such a list for the
     world-wide Internet (or, indeed, for any large "enterprise" network) has proven to be pro-
     hibitive, so the Domain Name System (DNS) is used instead, except as noted.

     For each IP network a single line should be present with the following information:
	   name network [alias ...]

     These are:
	   name     Official network name
	   network  IP network number
	   alias    Network alias

     Items are separated by any number of blanks and/or tab characters.  A ``#'' indicates the
     beginning of a comment; characters up to the end of the line are not interpreted by routines
     which search the file.

     Network number may be specified in the conventional dot (``.'') notation using the
     inet_network(3) routine from the IP address manipulation library, inet(3).  Network names
     may contain "a" through "z", zero through nine, and dash.

     IP network numbers on the Internet are generally assigned to a site by its Internet Service
     Provider (ISP), who, in turn, get network address space assigned to them by one of the
     regional Internet Registries (e.g. ARIN, RIPE NCC, APNIC).  These registries, in turn,
     answer to the Internet Assigned Numbers Authority (IANA).

     If a site changes its ISP from one to another, it will generally be required to change all
     its assigned IP addresses as part of the conversion; that is, return the previous network
     numbers to the previous ISP, and assign addresses to its hosts from IP network address space
     given by the new ISP.  Thus, it is best for a savvy network manager to configure his hosts
     for easy renumbering, to preserve his ability to easily change his ISP should the need
     arise.

FILES
     /etc/networks  The networks file resides in /etc.

SEE ALSO
     getnetent(3), nsswitch.conf(5), resolv.conf(5), hostname(7), dhclient(8), dhcpd(8), named(8)

     Classless IN-ADDR.ARPA delegation, RFC 2317, March 1998.

     Address Allocation for Private Internets, RFC 1918, February 1996.

     Network 10 Considered Harmful, RFC 1627, July 1994.

     Classless Inter-Domain Routing (CIDR): an Address Assignment and Aggregation Strategy, RFC
     1519, September 1993.

     DNS Encoding of Network Names and Other Types, RFC 1101, April 1989.

HISTORY
     The networks file format appeared in 4.2BSD.

BSD					November 17, 2000				      BSD
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