NAME

       netmask - a netmask generation and conversion program

SYNOPSIS

       netmask [ options ] spec [ spec ... ]

DESCRIPTION

       This program accepts and produces a variety of common network address and netmask formats.
       Not only can it convert address and netmask notations, but it will optimize the  masks  to
       generate  the  smallest  list  of  rules.   This is very handy if you've ever configured a
       firewall or router and some nasty network administrator before you decided  that  base  10
       numbers were good places to start and end groups of machines.

OPTIONS

       -h, --help
              Print a summary of the options

       -v, --version
              Print the version number

       -d, --debug
              Print status/progress information

       -s, --standard
              Output address/netmask pairs

       -c, --cidr
              Output CIDR format address lists

       -i, --cisco
              Output Cisco style address lists

       -r, --range
              Output ip address ranges

       -x, --hex
              Output address/netmask pairs in hex

       -o, --octal
              Output address/netmask pairs in octal

       -b, --binary
              Output address/netmask pairs in binary

       -n, --nodns
              Disable DNS lookups for addresses

DEFINITIONS

       A spec is an address specification, it can look like:

       address
              One address.

       address1:address2
              All addresses from address1 to address2.

       address1:+address2
              All addresses from address1 to address1+address2.

       address/mask
              A group starting at address spanning mask.

       An address is an internet network address, it can look like:

       ftp.gnu.org
              An internet hostname.

       209.81.8.252
              A standard dotted quad internet address notation.

       100    A decimal number (100 in this case).

       0100   An octal number preceded by "0" (64 in this case).

       0x100  A hexadecimal number preceded by "0x" (256 in this case).

       A mask is a network mask, it can look like:

       255.255.224.0
              A dotted quad netmask (netmask will complain if it is not a valid netmask).

       0.0.31.255
              A Cisco style inverse netmask (with the same checks).

       8      The number of bits set to one from the left (CIDR notation).

       010    The number of bits set to one from the left in octal.

       0x10   The number of bits set to one from the left in hexadecimal.

AUTHOR

       netmask  was written by Robert Stone.  Some algorithm design and optimization was provided
       by Tom Lear.  This manual page was written by Robert Stone.

BUGS

       Let me know if you find any.  This man page is a bit more simplistic than  I'd  like,  but
       I've forgotten most of the groff I once knew.

SEE ALSO

       ipchains(1), ipfwadm(8), netstat(8), route(8), routed(8), gated(8), tcpd(8)