wildcard masks

Unanswered Question
Aug 29th, 2007

Hi all, can anyone tell me how we work out what the wildcard mask is ?


I have this problem too.
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royalblues Wed, 08/29/2007 - 05:43

A simple method would be to subtract the subnet mask from

eg. if you need to know the wildcard mask for then you can do - =

HTH, rate if it does


mohammedmahmoud Wed, 08/29/2007 - 05:44

hi Carl,

Wildcard mask is a bit matcher which is the inverse logic of the subnet mask (a subnet mask of corresponds to a wildcard of, just inverse the binary 1s to 0s and vice versa) -> 0 = match and 1 = ignore, accordingly a wildcard of = host, since all bits must match , and = any, since we don't care what any bit is.


Mohammed Mahmoud.

massimiliano.se... Wed, 08/29/2007 - 05:46


The wildcard mask is an "inverse mask", that is: bit 0 means "care" and bit 1 means "don't care".

An example of application is an access list:

access-list 100 deny

Conversion in binary -> 00000000.00000000.00000000.00001111 -> 11000000.10101000.00000001.0000000

The interval of denied addresses is:

From 11000000.10101000.00000001.00000000 to 11000000.10101000.00000001.00001111

In decimal

From to

That is all addresses from to are denied.

I hope this helps.

Best regards.



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