An engineer must configure a ACL that permits packets which include an ACK In the TCP header. Which entry must be Included In the ACL?
A. access-list 110 permit tcp any any eq 21 tcp-ack
B. access-list 10 permit ip any any eq 21 tcp-ack
C. access-list 10 permit tcp any any eq 21 established
D. access-list 110 permit tcp any any eq 21 established
Answer:D
An engineer must configure a ACL that permits packets which include an ACK In the TCP header. Which entry must be Included In the ACL?
A. access-list 110 permit tcp any any eq 21 tcp-ack B. access-list 10 permit ip any any eq 21 tcp-ack C. access-list 10 permit tcp any any eq 21 established D. access-list 110 permit tcp any any eq 21 established
Explanation: The established keyword is only applicable to TCP access list entries to match TCP segments that have the ACK and/or RST control bit set (regardless of the source and destination ports), which assumes that a TCP connection has already been established in one direction only. Let’s see an example below: