I recently set up a cisco 3560g switch and connected it to my network. Everything was fine while I did a little testing. This sat there just fine for a couple of days while I did other things. I then put 2 esxi 5.5 servers on the switch. They are both Dell R710 servers. I connected all 4 gig ethenets on both servers to the switch. For each server I set up 2 etherchannels. One for front end traffic and one for backplane and nas traffic. Everything looked great. I had to tweak the Management Network to use IP hash like the virtual switch it was connected to but other than that it was all very smooth. The problem came a few hours later. Two of my core switches started complaining that a specific mac address started flapping between two ports. One of the ports was the trunk to the new switch and the other port was to the switch where mac address belongs. The real strange part is that while the vlan that the mac address is on is allowed on the new switch there was nothing using it. There were no virtual machines using it. The vlan wasn't even set up in any of the vswitches in ESXi. There are many other vlans available on that switch but only one was affected and just like many other vlans, that one wasn't used anywhere on the switch. To fix the issue I removed the etherchannels and dropped back to Port ID load balancing instead of IP Hash. The problem has gone away.
Does anyone have any ideas why a switch or esxi would start trying to take over a mac address on a vlan that is not in use on the switch or esxi box while using etherchannel?
The switch has Cisco IOS Software, C3560 Software (C3560-IPSERVICESK9-M), Version 15.0(2)SE5, RELEASE SOFTWARE (fc1).
The ESXi servers are 5.5.0, 2302651.
Thanks
Mark
