whatmask man page

whatmask — Subnet mask notation conversion tool.

Syntax

whatmask <netmask or ip/netmask>
see the Examples section below

Description

Whatmask is a small C program that will help you with network settings.

Whatmask can work in two modes. The first mode is to invoke Whatmask with only a subnet mask as the argument. In this mode Whatmask will echo back the subnet mask in four formats, plus the number of useable addresses in the range.

Netmask Notations supported:

 Name                  Example

 CIDR                         /24
 Netmask            255.255.255.0
 Netmask (hex)         0xffffff00
 Wilcard Bits           0.0.0.255

The above notations are all identical. CIDR notation commonly has a "/" in front of the number (representing the number of bits). Whatmask can accept these notations with or without a slash. This notation is used more and more recently. A lot of popular routers and software support this notation.

Netmask notation is pretty much the standard old-school way of doing it. It is supported by most systems (Un*x, Win, Mac, etc.).

Netmask (Hex) is the hexadecimal representation of the netmask. Many implementations of ifconfig use this notation

Wilcard Bits are similar to the netmask, but they are the logical not of the netmask. This notation is used by a number of popular routers (and nobody knows why...).

To use Whatmask in the first mode simply type "whatmask <notation>" The  notation can be in any of the four formats and Whatmask will automagically figure out what it is and display all four notations.

To use Whatmask in its second mode execute Whatmask with any ip address within the subnet, followed by a slash ('/'), followed by the subnet mask in any format. (e.g. 192.168.0.23/255.255.255.224, or 192.168.0.23/27) Put no spaces in the argument.

Whatmask will echo back the following:

- The netmask in the following formats: CIDR, Netmask, Netmask (Hex), Wildcard Bits
- The Network Address
- The Broadcast Address
- The number of Usable IP Addresses
- The First Usable IP Address
- The Last Usable IP Address

(Whatmask assumes that the Broadcast address is the highest address in the subnet. This is the most common configuration.)

Options

<no options> see above and below for usage.

Examples

Examples of how Whatmask works:

	myhost> whatmask /26
	
	---------------------------------------------
		   TCP/IP SUBNET MASK EQUIVALENTS
	---------------------------------------------
	CIDR = .....................: /26
	Netmask = ..................: 255.255.255.192
	Netmask (hex) = ............: 0xffffffc0
	Wildcard Bits = ............: 0.0.0.63
	Usable IP Addresses = ......: 62
	
	myhost> whatmask 255.255.192.0
	
	---------------------------------------------
		   TCP/IP SUBNET MASK EQUIVALENTS
	---------------------------------------------
	CIDR = .....................: /18
	Netmask = ..................: 255.255.192.0
	Netmask (hex) = ............: 0xffffc000
	Wildcard Bits = ............: 0.0.63.255
	Usable IP Addresses = ......: 16,382
	
	myhost> whatmask 0xffffffe0
	
	---------------------------------------------
		   TCP/IP SUBNET MASK EQUIVALENTS
	---------------------------------------------
	CIDR = .....................: /27
	Netmask = ..................: 255.255.255.224
	Netmask (hex) = ............: 0xffffffe0
	Wildcard Bits = ............: 0.0.0.31
	Usable IP Addresses = ......: 30
	
	myhost> whatmask 0.0.0.31
	
	---------------------------------------------
		   TCP/IP SUBNET MASK EQUIVALENTS
	---------------------------------------------
	CIDR = .....................: /27
	Netmask = ..................: 255.255.255.224
	Netmask (hex) = ............: 0xffffffe0
	Wildcard Bits = ............: 0.0.0.31
	Usable IP Addresses = ......: 30
	
	myhost> whatmask 192.168.165.23/19
	
	------------------------------------------------
			   TCP/IP NETWORK INFORMATION
	------------------------------------------------
	IP Entered = ..................: 192.168.165.23
	CIDR = ........................: /19
	Netmask = .....................: 255.255.224.0
	Netmask (hex) = ...............: 0xffffe000
	Wildcard Bits = ...............: 0.0.31.255
	------------------------------------------------
	Network Address = .............: 192.168.160.0
	Broadcast Address = ...........: 192.168.191.255
	Usable IP Addresses = .........: 8,190
	First Usable IP Address = .....: 192.168.160.1
	Last Usable IP Address = ......: 192.168.191.254
	
	myhost> whatmask 192.168.0.13/255.255.255.0
	
	------------------------------------------------
			   TCP/IP NETWORK INFORMATION
	------------------------------------------------
	IP Entered = ..................: 192.168.0.13
	CIDR = ........................: /24
	Netmask = .....................: 255.255.255.0
	Netmask (hex) = ...............: 0xffffff00
	Wildcard Bits = ...............: 0.0.0.255
	------------------------------------------------
	Network Address = .............: 192.168.0.0
	Broadcast Address = ...........: 192.168.0.255
	Usable IP Addresses = .........: 254
	First Usable IP Address = .....: 192.168.0.1
	Last Usable IP Address = ......: 192.168.0.254
	
	myhost> whatmask 192.168.0.113/0xffffffe0
	
	------------------------------------------------
			   TCP/IP NETWORK INFORMATION
	------------------------------------------------
	IP Entered = ..................: 192.168.0.113
	CIDR = ........................: /27
	Netmask = .....................: 255.255.255.224
	Netmask (hex) = ...............: 0xffffffe0
	Wildcard Bits = ...............: 0.0.0.31
	------------------------------------------------
	Network Address = .............: 192.168.0.96
	Broadcast Address = ...........: 192.168.0.127
	Usable IP Addresses = .........: 30
	First Usable IP Address = .....: 192.168.0.97
	Last Usable IP Address = ......: 192.168.0.126
	
	myhost> whatmask 192.168.0.169/0.0.0.127
	
	------------------------------------------------
			   TCP/IP NETWORK INFORMATION
	------------------------------------------------
	IP Entered = ..................: 192.168.0.169
	CIDR = ........................: /25
	Netmask = .....................: 255.255.255.128
	Netmask (hex) = ...............: 0xffffff80
	Wildcard Bits = ...............: 0.0.0.127
	------------------------------------------------
	Network Address = .............: 192.168.0.128
	Broadcast Address = ...........: 192.168.0.255
	Usable IP Addresses = .........: 126
	First Usable IP Address = .....: 192.168.0.129
	Last Usable IP Address = ......: 192.168.0.254

Bugs

Report bugs to <software@laffeycomputer.com>

Contributors

Original code:

Joe Laffey <software@laffeycomputer.com>

Assistance with Manpage and Packaging:

David Wirch <kuma@linuxboxen.org>

Many thanks to the beta testers and users who sent in valuable feedback!

Updates

Official Whatmask website:

Info

Nov 14, 2003 LAFFEY Computer Imaging Network