I was wondering what damages to equipment people have observed from lightning activity. In particular, is it possible for lightning to damage cat5 cable without smoking the attached devices, and is it possible for particular interfaces on a router to be damaged without the whole router being affected.
I've had clients and colleagues who have had particular components destroyed by lightning strikes while other components inside the same devices (servers, network infrastructure, etc) remain untouched. Usually this type of damage is the result of smaller power surges, though. Lightning is quite a bit less forgiving, but it depends on how far down the line the strike occurs. Usually the strikes that have hit the data center building itself, or real close to it, do quite a bit of damage even through power protection equipment.
All kinds of things can happen as the result of a lightning strike including the specific cases that you mention, although it's rare and you're extremely lucky if only your cat5 gets smoked with nothing else attached to it getting damaged as well. A router interface getting blown out without damage to anything further inside is also possible, but again somewhat unlikely.
After a lightning strike where you have confirmed damage you should place anything damaged under full suspect and run complete diagnostics on the device(s).