Networking - Security - Discussion

Discussion :: Security - Security (Q.No.12)

12. 

You want to create a standard access list that denies the subnet of the following host: 172.16.198.94/19. Which of the following would you start your list with?

[A]. access-list 10 deny 172.16.192.0 0.0.31.255
[B]. access-list 10 deny 172.16.0.0 0.0.255.255
[C]. access-list 10 deny 172.16.172.0 0.0.31.255
[D]. access-list 10 deny 172.16.188.0 0.0.15.255

Answer: Option A

Explanation:

First, you must know that a /19 is 255.255.224.0, which is a block size of 32 in the third octet. Counting by 32, this makes our subnet 192 in the third octet, and the wildcard for the third octet would be 31 since the wildcard is always one less than the block size.

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