Every so often you come across a problem that makes you dredge the contents of the grey matter for an answer. I had one this week.
The client's server room had a cabinet with seven 24-port switches and no cable management. So there were scores of cables in a mass of spaghetti, and we had to find the uplinks between three of the seven. Needless to say, the colour scheme was cunningly designed (grey for server connections, grey for phone connections and grey for uplinks). Admittedly the grey phone cables had blue stickers on, but many had fallen off. It was literally impossible to get to some connections in order to follow the cable to its other end.
How do you find an uplink cable other than by looking at it? Well, on a managed switch the management interface gives you the answer. Look at the MAC address list for each port; if it's got a single address, it's a connection to a computer; if it's got lots, the chances are it's an uplink to another switch. Five minutes later we were re-patched appropriately (the task for the day was to split the network into two chunks so we could put traffic shaping on part of it).
Oh, and it goes without saying that to throw us off the scent, one of the uplinks had been made with a cable with a blue sticker - don't you just love it when that happens?
The morals of the story, then, are twofold. First, have proper cable colour coding and management - you'll thank yourself one day. And second, take a step back from any problem and ask if there's any route to an answer other than the obvious one.