Laffey Computer Imaging

whatmask - from Laffey Computer Imaging

Price: $0 (GPL License)

Current Version: 1.2

Date Modified: Nov. 14, 2003

Overview

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

See an online demo here, or here.
See below for documentation on what to enter. These demo sites pipe the form input to Whatmask.
(Sites not endorsed or controlled by LAFFEY Computer Imaging)

Details

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... ... actually I found a great explanation from 'billf' who removed the nobody knows why line from the FreeBSD port: Netmasks are contiguous bits, wildcard masks don't need to be).

To use Whatmask in the original 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 find out more about subnets and netmasks see the References section below.

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)

Whatmask will echo back the following:

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

 

Examples

	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

COMPILATION NOTE: Some users have reported problems with pre-release versions of gcc. If you get "illegal instruction" errors please try compiling with an official full release of your compiler. You may also try disabling the optimizer by removing "-O2" from the Makefile after running configure.

 


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Source

Binaries


Revision History


v1.2


v1.1


v1.0

References

O'Reilly and Assocaites:
TCP/IP Network Administration, 2nd Edition
By Craig Hunt
2nd Edition December 1997
1-56592-322-7

Cisco - IP Addressing and Subnetting for New Users

More info on wilcard bits and Cisco routers.

Then of course you can do a net search... I like Google

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