FAQ: 'no ip domain lookup' vs 'transport preferred none'

An easy but a very frequent question: "how to prevent DNS lookup for mistyped IOS commands?"

The frequent answer is: "Yes, it's annoying. Use 'no ip domain lookup' or 'transport preferred none'"
But be careful! Both command will work. Still 'no ip domain lookup' turns off DNS. Usually it's not a good idea for production router. Just imagine, what if you'll have to use 'ping cisco.com' urgently? =)

On the other side 'transport preferred none' prevents your router from session spawn to 'dfgfsdg' or 'x.x.x.x' without 'telnet' or 'ssh' keywords. But you'll be able to use 'ping cisco.com'.

So the right answer is: "Use 'transport preferred none'. And please forget about 'no ip domain lookup'!"

PS: Do not confuse 'no ip domain lookup' global configuration mode command and 'no domain-lookup' line configuration command. The latter will not stop DNS resolution for all commands, only for show output, traceroute, etc.