Whilst troubleshooting an issue with a server, it was noticed that the link from one of the interfaces which should have been connecting at gigabit speed, was only connecting at 100 Mbps.  Both the server interface and switch interface were set to autonegotiate.  The server interface was reset, but it did not fix the problem.  A new cable was installed and VOILA!  Gigabit speeds.  Upon examination of the removed cable, which was a premade cable, it was noticed that two wires were switched.

So if you’re having a problem getting a link to run at gigabit speeds, don’t rule out the cable, even if it is new out of the bag!