What is telnet ?

While being one of the most unsecure protocols, due to it’s transfer of passwords in cleatext, this is one of the most useful and widely used protocols/applications.

How can you connect to a router using Telnet ?

First you need to configure the router to accept telnet logins by doing

line vty 0 4

password cisco

login

This will enable 5 simultaneous telnet logins to the router.

on smaller routers, configuration is accessed by connecting through a web browser. So telnet is not an option.