Netmask

You might also see: ipcalc

Description

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  this article.

Installation

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

Usage

Basic Syntax

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

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 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.: 10.0.0.1
  • hostname: dns domain name. E.g: mail.google.com

• A mask ca be any of:
  • A dotted quad netmask (netmask will complain if it is not a valid netmask). E.g.: 255.255.224.0
  • A Cisco style inverse netmask (with the same checks). E.g.: 0.0.31.255
  • 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

Examples

$ netmask aldeid.com
  80.14.163.161/32

$ netmask -s aldeid.com
  80.14.163.161/255.255.255.255

$ netmask -s 192.168.100.1:192.168.100.20
  192.168.100.1/255.255.255.255
  192.168.100.2/255.255.255.254
  192.168.100.4/255.255.255.252
  192.168.100.8/255.255.255.248
 192.168.100.16/255.255.255.252
 192.168.100.20/255.255.255.255

$ netmask 192.168.100.1:192.168.100.20
  192.168.100.1/32
  192.168.100.2/31
  192.168.100.4/30
  192.168.100.8/29
 192.168.100.16/30
 192.168.100.20/32