[afnog] DHCP configuration on cisco router 2600 series

[Philip Smith]

Mark Tinka said the following on 8/9/05 22:52:
>
> Oh, and as we always recommend at the AfNOG workshops, 
> unless you really need it, turn off DNS name resolution 
> on the router:
> 
> conf t
>  no ip domain-lookup

line con 0
 transport preferred none
line vty 0 4
 transport preferred none

is what you want...

> This will solve the problem you are seeing when the 
> router software detects arguments or options it isn't 
> familiar with.

...to achieve this.

If you type in something at the command prompt and it isn't a command
the router recognises, the router will by default try all supported
transports. This includes IP transport, so the first action will be to
look the "name" up in the DNS. Disabling DNS lookups only stops the name
lookup, it doesn't stop the router hunting through other configured
transports before giving an error. Furthermore, disabling domain lookup
means that traceroutes etc from the router don't resolve into names,
making troubleshooting that much harder.

So the preferred way is to leave domain lookups active, but disable the
preferred transport, as I documented above. Wish it was the default...
Also wish that domain-lookups were disabled by default... etc... :(

philip
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