I have two colo cabinets with a couple of crossconnects running between them. In one, I have two 2970s. In the other, a piece of crap Netgear and a 2950 that was never configured.
I started seeing some weird ARP broadcasts and IP addresses in a subnet I do not use. It's coming from the crossover that goes to the Netgear. So, I thought i'd replace that Netgear with another 2970. I configured it, plugged it in, let IOS boot, and moved everything from the Netgear to the Cisco... and all hell broke loose. Oops, VLAN mismatch warnings, and no traffic. I put every port on this new 2970 into the same VLAN as the one I'm dealing with on the other side. Still no go. So I configure one port on each as a trunk using ISL. That worked with a cable dragged across the floor, but when I went back to the crossconnect, it just never worked. The link light did change from orange to green, but no traffic ever crossed it.
The long cable I was using is a crossover, if that makes any difference.
I gotta go back in later tonight and try again, when there isn't as much traffic on the network. Holy God, a minute takes about 18 years when your pager and phone are ringing off the hook! :-) Other than the ~15 seconds it takes for the ports on the 2970 to synch up... what other gotchas are there in repacing a switch like this? Should I clear the ARP tables on both sides as well?