Monday, April 18, 2011

Disable DNS Lookup on Cisco Routers and Switches

This article discusses how you can disable DNS lookup on Cisco routers and switches and effect when DNS lookup is enabled.

Problem
In privilege EXEC mode, if you type in something other than a Cisco IOS command, the router assumes that you typed a domain name and it tries to resolve what ever you type.

Although this feature is can be useful in some situations, for most of the time, this is a pain, especially if you do not have DNS server configured. The router becomes irresponsive for about 5-6 seconds trying to resolve the name.

The following is an example.
R4#wrong-command
Translating "wrong-command"...domain server (255.255.255.255)
 (255.255.255.255)
Translating "wrong-command"...domain server (255.255.255.255)

% Unknown command or computer name, or unable to find computer
address
R4#