Networking - Security - Discussion

Discussion :: Security - Security (Q.No.6)

6. 

What command will permit SMTP mail to only host 1.1.1.1?

[A]. access-list 10 permit smtp host 1.1.1.1
[B]. access-list 110 permit ip smtp host 1.1.1.1
[C]. access-list 10 permit tcp any host 1.1.1.1 eq smtp
[D]. access-list 110 permit tcp any host 1.1.1.1 eq smtp

Answer: Option D

Explanation:

When trying to find the best answer to an access-list question, always check the access-list number and then the protocol. When filtering to an upper-layer protocol, you must use an extended list, numbers 100-199 and 2000-2699. Also, when you filter to an upper-layer protocol, you must use either tcp or udp in the protocol field. If it says ip in the protocol field, you cannot filter to an upper-layer protocol. SMTP uses TCP.

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