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Whatmask is a small C program that will help you with network settings.
Whatmask can work in two modes. The first mode (which is how prior
versions worked) 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
Hex Netmask 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.).
Netmasks are sometimes represented as hexadecimal values, especially in
the BSDs.
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 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:
- The netmask in the following formats: CIDR, 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