You can set the identity of the router with the hostname command. This is only locally significant,which means that it has no bearing on how the router performs name lookups or how the router works on the internetwork.
Here’s an example
Router#config t
Enter configuration commands, one per line. End with
CNTL/Z.
Router(config)#hostname debianadmin
debianadmin(config)#hostname london
london(config)#
Even though it’s pretty tempting to configure the hostname after your own name, it’s definitely a better idea to name the router something pertinent to the location. This is because giving it a hostname that’s somehow relevant to where the device actually lives will make finding it a whole lot easier. And it also helps you confirm that you are, indeed, configuring the right device.