CompTIA Network+ N10-006 Q404

Joe, a network administrator, has installed an SFTP server behind a load-balancing router. He opened port 21 but was unable to establish a connection. Which of the following ports should he have opened?

A. Port 20
B. Port 22
C. Port 162
D. Port 443

Correct Answer: B

Explanation/Reference:
https://en.wikipedia.org/wiki/SSH_File_Transfer_Protocol