If an ACL rule permits TCP traffic from 172.18.20.0 to 172.18.20.32 for FTP, how would a packet from 172.18.20.14 to 172.18.20.40 with a protocol of 21 be treated?

The rule in the Access Control List (ACL) permits TCP traffic for FTP, which uses port 21. The specified source IP range is from 172.18.20.0 to 172.18.20.32. When a packet originates from 172.18.20.14 and is directed to 172.18.20.40, it is important to consider both the source and destination IP addresses along with the protocol being used.

In this scenario, packet inspection reveals that the source address (172.18.20.14) falls within the permitted range of 172.18.20.0 to 172.18.20.32, thus satisfying the source condition of the ACL rule. Although the destination IP (172.18.20.40) does not fall within the permitted range, the critical factor here is that the ACL specifically permits TCP traffic for FTP (port 21) from the defined source range.

Since the packet from 172.18.20.14 uses the FTP protocol (port 21), it matches the type of traffic defined in the ACL. Given that the ACL permits this traffic based on the source IP and the protocol, the packet will be permitted through the ACL.