How to Change the router’s host name - Cisco Router

Enter configuration mode using the following command:

Router#configure terminal

Change the host name of the router to RouterA using the following command :

Router(config)#hostname RouterA
RouterA(config)#

Notice how changing the hostname immediately affects the prompt. Remember that you are configuring the running configuration.

_________________________________________________________________________________

Thanks to  http://techgurulive.com/2009/04/29/how-to-change-the-routers-host-name-cisco-router/