VMs (including vCenter) disconnected after vMotion to any host
Article ID: 418832
Updated On:
Products
Issue/Introduction
A given VM, including the vCenter VM, becomes disconnected after being migrated or a vMotion to any other host in an environment.
The issue is consistent and happens after a migration or vMotion 100% of the time, though not all VMs may be impacted at the same time.
Note: If the issue is intermittent, or only disconnects after a vMotion on some occasions, this KB may still apply, but the following KB may be more applicable: VMs intermittently lose network connections after vMotion
Environment
vCenter (all versions)
Cause
After a vMotion operation, the receiving host sends a Reverse ARP (RARP) packet on behalf of the VM to update the rest of the network of the VM's new location.
In some cases, although the RARP can be confirmed as leaving the host as expected via packet captures, the updated VM location information is not propagated through the network by the physical switch and so any further communication to/from the VM is dropped since the network location is now incorrect.
Resolution
The issue is with the physical network not updating the location information correctly, so the physical networking team should be engaged to investigate the behavior.
Additional Information
You can use the built-in pktcap-uw tool to set up a capture on the destination host at the time of a vMotion to ensure the RARP packet is being sent out, though it may become complicated to preemptively set up the capture as variables such as the uplink the VM will use after the vMotion may vary based on configurations. That said, the below KB details the pktcap-uw tool for reference, but it may be worthwhile to create a case with Broadcom Support for assistance: Creating and managing Broadcom support request (SR) cases
NOTE: To see RARP packets specifically, the packet capture will need to be exported to a packet capture file (.pcapng) and then reviewed with a tool such as Wireshark, filtering for "arp" packets in the tool itself rather than in the capture command:
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