Follow these directions to assign a domain name to a Cisco router in IOS.
Use the show running-config to verify that the domain name has changed.
The reload command can be used to return the switch to the configuration it had before any changes were made.
To ensure these changes remain saved if the router is restarted, save the changes to the startup-config. Type copy running-config startup-config and press enter. This saves to NVRAM. To ensure the startup-config contains the new domain name, use the show startup-config command. It is also possible to save the changes to flash using the copy startup-config flash command. Then use the show flash command, and the startup-config file should be listed.