VM Mac Address Shows Up on physical vMotion Switch Port

[jefflf]

Our Network group monitors MAC addresses that show up on their physical switch ports and if they see a MAC address that they don't have registered to that physical port in their database, they generate a Help Desk ticket and threaten to shut the physical port down. I've tried searching online for why this is happening and I've opened a ticket with VMware, all to no avail. Do any of you ever experience this issue, or perhaps know why this is happening? The issue is transient so I'm thinking it has something to do with vMotion.

We're being told that this is happening on each of our ESXi 5.5 hosts, which all have 1 dedicated vMotion vSwitch with 1 dedicated NIC hooked up to a non-routing VLAN.

[bspagna89]

Hi Jeff,

I believe the ESX host sends out a GARP or RARP (not sure which one) basically letting the network know that the VM now lives on Switch B instead of Switch A. This usually happens when the vMotion has completed.

You can test this by changing the setting  "Notify Switches" In your vSwitch to "No". Change that setting and then perform a vMotion and ask your network team to monitor and see if the MAC address shows up. I'd recommend leaving this setting"Yes" as 1. It updates the network when a VM is moved and or Powered on. 2. Notifies switches when there are updates regarding uplink changes (if one fails, how to reach a VM etc).

[jefflf]

Excellent! Thank you so much for the insight.

[bspagna89]

glad to be of assistance! If you feel the answer was what you were looking for, you can mark it as correct/helpful that would help others out who search for something similar.

[jonedved]

This is correct, after vMotion is complete successfully, a notification will be sent to the switch (by default Notify switch option is selected)

However - that should not be happening on the vMotion port. The vMotion port is only used to copy the machine state between two servers!

Notification will go out on the VM port group on which your VM has virtual interfaces.

If you see VM MAC address on that port, then you need to verify your server configuration. Do you have a separate vSwitch for vMotion? Are there any VM port groups on the same vSwitch?