I bring a question to the folks here on the forums to try and help me explain a wrinkle I recently encountered with respect to wildcard masks…
Now, as I understood wildcard masks, they behave similary to subnet masks in that as you start placing bits in the mask, it works (for subnets) as a contiguous placement from left to right.
Example: 255.255.255.224
11111111.11111111.11111111.11100000
You cannot have something like:
Example: 255.255.224.192
11111111.11111111.11100000.11000000
Now for wildcard masks (and I refer to them when used in Cisco Access Control Lists) they simply work right to left.
Example: 0.0.7.255
00000000.00000000.00000111.11111111
However, I encountered on a Cisco exam a question that would challenge this assumption. The wildcard mask I was given to work with was 0.0.7.254! I must confess that while I am not fluid with wildcard masks, I do understand their basic mechanics – except for this.
Can anyone suggest a method of logic of how this mask would be utilized to filter a particular subnet?
