Disable DNS Lookup on Cisco Routers and Switches

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#

Solution
To disable domain look up type the commands as shown billow.

R4#conf t Enter configuration commands, one per line.  End with CNTL/Z. R4(config)#no ip domain-lookup R4(config)#

Now the output is quick and router does not become irresponsive

R4#wrong-command Translating "wrong-command"   Translating "wrong-command"   % Unknown command or computer name, or unable to find computer address R4#