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File Formats                                          networks(4)

     networks - network name database



     The networks file is a local source of information regarding
     the networks which comprise the Internet. The networks  file
     can be used in conjunction with, or instead of,  other  net-
     works  sources,  including the NIS maps  networks.byname and
     networks.byaddr and the NIS+ table  networks.  Programs  use
     the  getnetbyname(3SOCKET)  routines to access this informa-

     The network file has a single line for  each  network,  with
     the following information:

     official-network-name network-number aliases

     Items are separated by any number of  SPACE or  TAB  charac-
     ters. A `#' indicates the beginning of a comment. Characters
     up to the end of the line are not  interpreted  by  routines
     which  search  the  file. This file is normally created from
     the official network  database  maintained  at  the  Network
     Information  Control  Center (NIC), though local changes may
     be required to bring it  up  to  date  regarding  unofficial
     aliases and/or unknown networks.

     Network numbers may be specified  in  the  conventional  dot
     (`.')  notation  using  the  inet_network  routine  from the
     Internet address  manipulation  library,  inet(7P).  Network
     names may contain any printable character other than a field
     delimiter, NEWLINE, or comment character.

     getnetbyaddr(3SOCKET), getnetbyname(3SOCKET), inet(3SOCKET),
     nsswitch.conf(4), inet(7P)

     The  official  SVR4   name   of   the   networks   file   is
     /etc/inet/networks.  The  symbolic link /etc/networks exists
     for BSD compatibility.

     The network number in networks database is the host  address
     shifted  to the right by the number of 0 bits in the address
     mask. For example, for the address that  has  a
     mask  of  fffffe00,  its  network number is 803351.  This is
     obtained when the address is shifted right by  9  bits.  The
     address  maps to 12.66.23. The trailing 0 bits should not be

SunOS 5.9           Last change: 17 Jan 2002                    1

File Formats                                          networks(4)

     specified.  The network number here is different  from  that
     described  in  netmasks(4).  For  this example, the entry in
     netmasks would be

SunOS 5.9           Last change: 17 Jan 2002                    2