Host 0003.ff88.ea48 in vlan 2 is flapping between port Fa0/7 and port Gi0/1

[Greg Wrobel]

I have a user who runs VM on his workstation, and this is the error switch logs:

Host 0003.ff88.ea48 in vlan 2 is flapping between port Fa0/7 and port Gi0/1

I'm pretty sure it has something to do with that VM.

The error is marked as warning, so I don't think that it is critical for normal operation; but how can I fix it.

Thanks!

[boss.silva]

Hello,

Probably the host has two or more NICs, and since one interface is GigabitEthernet, i assume it is the other switch that the host is connected. Some load balancing techniques can send traffic to both ports, and that would cause the switch to go crazy, since it is receiving traffic from the same MAC on two or more different ports.

Of course, this is for a one-mac scenario. If you are getting the behaviour for a lot of other MACs, that most likely is a layer 2 loop.

Regards,

Bruno Silva.

[Greg Wrobel]

It actually happens on 3 switches. The MAC address matches the address of the virtual machine on one of the computers. Any advice??

[RICHARD MESSINGER]

My first thought is along the lines of the VM doing some kind of load balancing.

What you probably do not have is any etherchannel configured on the switches.

You should look into using LACP between the switch and the VM interfaces.

[Greg Wrobel]

Faound the problem. Two virtual machines on two different computers with the same MAC address.