What will a network administrator likely need to reconfigure if a firewall is blocking traffic?

In the scenario where a firewall is blocking traffic, it is essential for a network administrator to identify which protocols and ports are being utilized by the applications in question. The key to resolving traffic blockage by a firewall is to ensure that the appropriate ports corresponding to the desired traffic type are configured correctly.

Focusing on the selected option, TCP port 20 is significant because it is associated with FTP (File Transfer Protocol) active mode data transfer. Although FTP control commands use TCP port 21, the actual data transfer for active FTP occurs over TCP port 20. If FTP traffic is being blocked, reconfiguring this port allows for proper data transmission.

Moreover, since the question specifies that there is a traffic blockage, addressing the configurations for this TCP port is crucial to enable FTP functionalities in a network environment. Without this reconfiguration, file transfers using FTP could fail, resulting in disruptions to users relying on the service.

Understanding the networking protocols and the ports they use is fundamental, and knowing which ports to adjust when encountering a firewall blockage is an essential skill for a network administrator.