Unlike other systems, where you enter a user ID and password to login – the Cisco router login is simply the act of starting up the console and hitting <Return> to go into User EXEC mode. This does not usually require an ID and password, since the User Exec commands are non-destructive.
Once you are logged into User mode, the EXEC command interpreter times out after 10 minutes of no input, and you will need to hit <Enter> to login again. You can disable the timer by either setting the interval to zero (in config mode):
exec-timeout 0
Or you can disable it altogether : no exec-timeout
To logout, simply type: logout