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You might also see: ipcalc


Netmask is a netmask generation and conversion program. It 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.

For more information on netmask, refer to Page in French this article.


Install netmask package:

$ sudo apt-get install netmask

Then optionally create a symbolic link in your /pentest/ directory:

$ mkdir -p /pentest/enumeration/netmask/
$ ln -s /usr/bin/netmask /pentest/enumeration/netmask/netmask


Basic Syntax

$ netmask [options] spec [spec...]


-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


  • A spec can be any of:
    • address: a single address
    • address1:address2: All addresses from address1 to address2
    • address:+address: All addresses from (address1) to (address1+address2)
    • address/mask: A group starting at address spanning mask
  • An address can be any of:
    • N: decimal number. E.g.: 100
    • 0N: octal number. E.g.: 0100
    • 0xN: hex number. E.g.: 0x100
    • N.N.N.N: dotted quad. E.g.:
    • hostname: dns domain name. E.g:
  • A mask ca be any of:
    • A dotted quad netmask (netmask will complain if it is not a valid netmask). E.g.:
    • A Cisco style inverse netmask (with the same checks). E.g.:
    • The number of bits set to one from the left (CIDR notation). E.g.: 8
    • The number of bits set to one from the left in octal. E.g.: 010
    • The number of bits set to one from the left in hexadecimal. E.g.: 0x10


$ netmask
$ netmask -s
$ netmask -s
$ netmask