- [Instructor] Another very useful global configuration
command is the no ip domain-lookup.
By default, when a command, and user, or enable mode
is entered into the switch
and the command is not recognized,
the switch thinks that the invalid command
is the name of a device that the user
is attempting to reach.
I'm going to show you how that works as I continue to talk.
So if I type enb, I hit enter, the switch thinks that enb
is the name of a device someplace on the network,
and it tries to resolve it, or look it up,
or match it to an IP address.
As such, this switch attempts to resolve this.
If it cannot find a lookup, on the switch itself,
it will send out a broadcast.
This can take several seconds for the switch prompt
to return while it waits for a response
from, hopefully, a DNS server.
And this can be very frustrating,
especially when you are trying to configure
to learn the configuration commands from the start,
and/or if you're not very good at typing.
You can see it takes quite a long time for this DNS lookup
to time out and return to the user prompt.
Finally, the switch will return to the user mode.
We want to disable this function,
so we type enable, we type config,
configure from the terminal and, again,
I'm hitting that tap key, enter and I type the command,
no ip domain-lookup, hit the tap key, enter,
that turns off the default desire of the switch
to resolve misspelled words into IP addresses.
I go ahead and hit exit,
takes me back out to the privileged mode,
exit back out to the user mode.