If an ACL entry permits TCP traffic from a specific source to a destination at a certain port, what will happen to a packet with a different protocol?

When an Access Control List (ACL) entry is configured to permit TCP traffic from a specific source to a destination on a designated port, it is specifically designed for TCP protocol packets. Therefore, any packet using a different protocol, such as UDP or ICMP, will not match this ACL entry because it does not meet the criteria set for TCP traffic.

In an ACL, when there is no explicit permit rule that matches a specific packet, the default action of the ACL applies. This default behavior is typically to deny any traffic that does not meet the defined conditions unless there is a corresponding permit statement for that type of traffic. As a result, packets that do not match the criteria for TCP traffic will be denied access according to the rules set forth in the ACL configuration.

This mechanism ensures that only the intended types of traffic are allowed through the network, enhancing security by preventing unauthorized or unwanted traffic types from passing through the network devices. Thus, the correct conclusion is that a packet with a different protocol will be denied.