vMotion fails after network configuration changes

Products

• VMware vCenter Server

Issue/Introduction

vMotion migration attempts may fail after a vCenter server patch, upgrade, or hardware maintenance. Symptoms include "Host is down" errors in migration logs and total loss of connectivity over the vMotion VMkernel adapter, despite host-level configurations being correct. This article addresses issues stemming from environmental network changes.

Environment

•  vSphere 7.0, 8.0, 9.0
• VMware Cloud Foundation (VCF) 4.x, 5.x.

Cause

This issue is typically environmental and not caused by the software upgrade itself. Common root causes include:

• VLANs used for vMotion (e.g., VLAN 404) not being properly tagged or allowed on physical switch trunk ports.
• Physical switch configuration changes (e.g., port pruning or access control lists) during maintenance.
• Inconsistent load-balancing or teaming policies across the cluster.

Resolution

1. Verify connectivity using vmkping: Run the following command to test vMotion network reachability: vmkping -I vmk1 <destination_IP>
2. Inspect VLAN configuration: Check if the required VLAN is tagged and allowed on the physical switch ports connected to the ESXi host uplinks.
3. Utilize CDP/LLDP info: Navigate to the ESXi host in vCenter (Configure > Networking > Physical Adapters) and retrieve the CDP/LLDP information. Provide this data to your networking administration team to verify that the upstream physical switch ports are correctly configured to trunk the vMotion VLAN.
4. Verify ESXi Firewall: Ensure that the "vMotion" service is enabled under Configure > System > Firewall for all hosts involved in the migration.
5. Review physical switch logs: Ask the network team to review physical switch logs for dropped packets or interface errors corresponding to the time of the vMotion failure.

Additional Information

• For further diagnostic assistance, refer to Testing VMkernel network connectivity with the vmkping command.
• For assistance with log retrieval, refer to the documentation on collecting support bundles.
• To speak with a support engineer, see Contact Support.