Wild Card Mask

Today I am going to tell about wild card mask which is also known as WCM. WCM refers to what needs to be permit and denied. Its all about 0's & 1's. Remeber one logic which cleary states that 0 means match the same and 1 means donot care. What it exactly means if you are adding 0 in your WCM entry it means corresponding to that octet in network address will be matched and if you are using 1 then corresponding to that octet in network address will be permit. Simpley we can say it is like mirroring which which check corresponding to its bits in the octet and take the decision on the basics of 0's and 1's.

Let's clear it with the help of an example:-
We need to permit the all host in network 192.168.1.0/24. For this we need to create an acl and wcm will be used here. It means we want first three octets i.e 192,168 & 1 remains the same and only last octet will be allowed to change. It means last octet can contains value starting from 0 to 255. Now create wcm for this

00000000.00000000.00000000.11111111

1st octet in wcm is having all zero, it will check its image in mirror and find 192 and it is not allowed to change,same is used for 2nd and 3rd octet. In the last octet all 1's are used and it will not check its image in mirror because everything is allowed in it. So at last you will be permitting 192.168.1.0,2,3,4,5.......and so on.


regards
shivlu jain

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