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no ip domain-lookup

One of the most annoying features of Cisco's IOS is the assuming that anything you type which is not a command is a hostname. So...

Translating "dev"...domain server (
Translating "dev"...domain server (

... and when you are configuring a router which either (a) does not have DNS, (b) is on a network that is down, or (c) is on the workbench and not actually connected to a network - you get to enjoy the long pause of a DNS timeout.


The solution is simple:

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

The "no ip domain-lookup" disables this feature. Now at least it fails instantly:

Translating "dev"
Translating "dev"
% Bad IP address or host name
% Unknown command or computer name, or unable to find computer address

The downside is that the router will no longer perform DNS look-ups to translate host names to addresses. That is bad for some specific use-cases [a VPN terminator is one possible example] - but generally that is not something that matters for a router. Once a router is configured you can always turn domain-lookup back on.

Note to self: every time you pull a router out of storage - do this first.

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