VMs lose network connectivity after vMotion/migration due to incorrect uplink teaming configuration
Article ID: 434979
Updated On:
Products
Issue/Introduction
- VMware vSphere Virtual Machines (VMs) randomly lose network connectivity during or immediately after a vMotion migration between ESXi hosts.
- Disabling and re-enabling the virtual Network Interface Card (vNic) occasionally restores network connectivity.
- A review of the dvSwitch ports reveals that the affected VM portgroups are improperly configured to use all available uplinks (Uplinks 1-4) as Active, conflicting with storage-dedicated uplinks.
endpoint | teamUplink | teaming name | vlan |
<REDACTED>_VM_Name>.eth0 | vmnic1 | Uplink1, Uplink2, Uplink3, Uplink4 | VLAN_<\Redacted>, VLAN_<\Redacted> |
vmk1 | vmnic1 | Uplink3 | dvpg_iscsi1-<\REDACTED> No VLAN |
vmk2 | vmnic3 | Uplink4 | dvpg_iscsi2-<\REDACTED> No VLAN |
Environment
- VMware vSphere ESXi - ANY
- VMware vCenter Server - ANY
Cause
The VM network portgroups are configured with all four uplinks set to "Active." However, uplinks 3 and 4 are dedicated strictly to storage traffic and are not trunked for virtual machine VLAN traffic. Following a vMotion, the virtual switch load balancing policy hashes the VM's MAC address to egress on either uplink 3 or 4, resulting in a Layer 2 traffic blackhole and immediate connectivity loss.
This also explains why disconnecting and reconnecting the vNic occasionally restores connectivity, as this operation will initiate a new hash calculation, potentially causing the VM to be mapped to an uplink configured for VM traffic.
Resolution
- Log in to the vSphere Client.
- Navigate to the Networking view and select the affected Distributed Virtual Switch.
- Right-click the impacted VM portgroup and select Edit Settings.
- Navigate to Teaming and failover.
- Under the Failover order, select the storage-dedicated uplinks (e.g., Uplink 3 and Uplink 4) and move them down to the Unused uplinks category.
- Click OK to save the configuration.
- Repeat this process for all VM portgroups that are improperly spanning the storage-dedicated uplinks.
Additional Information
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