Telnet is a client-server protocol, based on reliable connection-oriented transport. Typically, this protocol is used to establish a command-line interface connection to a remote device.

Telnet uses TCP port 23.

Telnet is easy to configure but not used often anymore since it is insecure, everything you do is sent in plaintext while SSH uses encryption. However, some older devices might only support Telnet, so it’s good to know how to configure it. Besides remote management, the Telnet client is also very useful to test access lists, routing, and to test if certain ports are listening or not.