What regex will match:

contains at least one instance of "1221", and no instances of "7474"

i.e. matches "7777 1221 4543"

but does not match "7777 1221 7474 4543"

I suspect I have to use negative lookaheads?

What regex will match:

contains at least one instance of "1221", and no instances of "7474"

i.e. matches "7777 1221 4543"

but does not match "7777 1221 7474 4543"

I suspect I have to use negative lookaheads?

I am using Cisco IOS (version: IOS XE 3.10.4S)