CompTIA 220-801 Certification Practice Test

Answer - A - The FTP uses ports 20 and 21 for its operation. If the users of a network need FTP access, ports 20 and 21 must be left unfiltered on the firewall.

Key Takeaway: File Transfer Protocol (FTP) is a standard network protocol used to exchange files over an Internet Protocol computer network. FTP servers use TCP port 21 to listen to incoming connections from clients. Data connections use port number 20. Make sure these ports are not filtered on the firewall.