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Wildcard Mask in ACL

Dear Sir/Colleagues,
I did my ACL assignment, but really got confused with all the questions with wildcard mask? Can you please clarify in which chapter it is covered the Wildcard mask?
And in the below question, please explain how the correct answer is 192.168.160.0.
Thanks in advance

You need to create an access list that will prevent hosts in the network range of 192.168.160.0 to 192.168.191.0. Which of the following lists will you use?

access-list 10 deny 192.168.160.0 255.255.224.0
access-list 10 deny 192.168.160.0 0.0.191.255
access-list 10 deny 192.168.160.0 0.0.31.255
access-list 10 deny 192.168.0.0 0.0.31.255

students Answer: access-list 10 deny 192.168.0.0 0.0.31.255

Correct answer: access-list 10 deny 192.168.160.0 0.0.31.255
Asked by Anil Pappachan | Aug 1, 2014 |  Reply now
Replies (1)
View CCNA Teacher 's Profile
Hi the range of 192.168.160.0 to 192.168.191.0 is a block size of 32. The network address is 192.168.160.0 and the mask would be 255.255.224.0, which for an access list must be a wildcard format of 0.0.31.255. The 31 is used for a block size of 32. The wildcard is always one less than the block size.

Aug 26, 2014