Bob, a new network consultant, is helping a business with their website updates. The firewall is in default deny mode, so he opens up port 21 to allow for FTP access to the webserver from the Internet. However, FTP still does not work. He notices that clients can connect, but cannot transfer any data. Why does FTP still not work?
A)FTP operates on port 23
B)FTP operates on port 25
C)FTP also uses port 20
D)FTP uses UDP which is connectionless

Question

Quizplus · Accepted Answer

FTP utilizes two TCP ports, 20 and 21. Port 21 is the control port that authenticates users and issues commands. Port 20 is the port on which the data is actually transferred.
Key Takeaway: FTP is a session oriented protocol and therefore uses TCP. TFTP uses UDP and is therefore connectionless and a lot less reliable. FTP always uses two ports. These ports are generally 20 and 21. Port 21 is the control channel responsible for authentication, issuing commands, and other administrative activities. Port 20 is generally the port on which the data is transferred. In passive mode, the server can negotiate another port other than 20 for data transfer.

Bob, a New Network Consultant, Is Helping a Business with Their