For the last two weeks I have been blaming BT for a problem with my network; ever since they had a broadband outage our BT hub has been playing up, dropping both wired and wireless connectivity inside the house every so often, and preventing Internet access. I have had to reset the hub and then reconfigure to get the network back up.
My home network is reasonably simple: I have a server as a Domain Controller which also does DHCP (gives out computer addresses). This is connected to a Gbit Switch, to allow fast communication between my wired computers, and the BT Hub is connected to that to give Wireless communications and Internet access.
Anyway I got fed up today and decided to put in one of my old wireless routers as the problem seemed to be related to the wireless part. As I was doing this I went through all the connections and that’s when I found I had plugged both ends of the same cable in to my switch while resetting after the first outage.
Result:- one switch doing a lot of chattering over that cable acting as a loopback and flooding the network causing the dropouts.