I have a 3560 switch and a 2960G switch. They are both in separate buildings, connected by Gigabit GBICs to an Allied Telesyn switch via separate fiber optic paths. When I connect the 2960G, the 3560 stops communicating with the network. There are no IP address conflicts, each switch has it's own IP. As soon as I disconnect the 2960G, the 3560 begins communicating again. The only configuration on the two CISCO switches are via the express setup GUI. Other than that, they have factory default settings. If anyone has any idea as to why this might be happening, I am all ears and very appreciative of your thoughts. Thanks you.