wildcard mask question

Oct 28, 2006 1 Replies

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max 19 years ago

Hi all,

I noticed a question in a CCNA lab for ACL's, it is as follows...

'Create an access list that will prevent the even numbered hosts from pinging but permit the odd numbered one.'

The answer is 'access-list 2 permit 192.168.14.1 0.0.0.254'

I understand wildcard masking but for the life of me i cant figure this answer :(

I know this is not a ccna forum but its the only place where i could think to get a decent answer.

Any help would be greatly appreciated.

Max

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Barry Margolin 19 years ago

Look at it in binary, where 254 is 11111110. This means that the low-order bit must match exactly, while the rest are don't-care. Any number with 0 in its low-order bit is even, 1 in its low-order bit is odd.

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