It seems like I can prune a trunk with more than one command. I'm not certain which I should be using.
switchport trunk allowed vlan add 1,2,3, ...etc.
switchport trunk pruning vlan add 1,2,3, ...etc.
Does the first simply specify which VLANs are *permitted* across a trunk (disallowing whatever you haven't identified), where the second actually disallows what you have specified (allowing all others)? Am I understanding that correctly?