How do you exit to domain server 255.255.255.255 on a cisco router?

Ctrl+Shift+6

This is the keyboard combination to stop the Domain Name Server translation as well as other things such as a ping in progress.

You can disable the domain name lookup by typing the following.

Router(Config)# no ip domain-lookup

This will cause anything that would otherwise trigger a domain name lookup to instead display

% Unknown command or computer name, or unable to find computer address