Post migration, the VMs may become unreachable on the network.

Products

• VMware vSphere ESXi

Issue/Introduction

• Checking the vNIC interface status from within the guest OS may report the link status to be down.
  
  
• If Linux, the guest OS /var/log/kern.log may report errors similar to the below:
  
  2025-10-07T07:52:39.009Z kernel - - - [402863.323027] NETDEV WATCHDOG: eth0 (vmxnet3): transmit queue 1 timed out
2025-10-07T07:52:39.010Z kernel - - - [402863.323041] WARNING: CPU: 5 PID: 0 at net/sched/sch_generic.c:477 dev_watchdog+0x25b/0x260
[....]
2025-10-07T07:52:39.085Z kernel - - - [402863.323319] vmxnet3 0000:03:00.0 eth0: tx hang
2025-10-07T07:52:39.085Z kernel - - - [402863.323445] vmxnet3 0000:03:00.0 eth0: resetting
2025-10-07T07:52:39.557Z kernel - - - [402863.331644] vmxnet3 0000:03:00.0 eth0: Failed to activate dev: error 1
  
  
• Affected VM's vmware.log report errors similar to the below:
  
  2025-10-07T07:52:40.198Z In(05) vcpu-5 - VMXNET3 user: Quiesce device 0.
2025-10-07T07:52:40.205Z In(05) vcpu-5 - VMXNET3 user: Activate device 0.
2025-10-07T07:52:40.206Z In(05) vcpu-5 - VMXNET3 user: failed to activate 'Ethernet0', status: 0xbad0014
2025-10-07T07:52:40.206Z In(05) vcpu-5 - VMXNET3 user: Activate request failed for device 0.
  
  
• In the ESXi host's /var/log/vmkernel.log, we may see that, at first, the port gets enabled. However, almost immediately, it gets disabled:
  
  2025-10-07T07:52:31.367Z In(182) vmkernel: cpu39:11080375)NetPort: 1618: enabled port 0x600014c with mac 00:50:xx:xx:xx:xx.
[....]
2025-10-07T07:52:31.367Z In(182) vmkernel: cpu39:11080375)ENS: Ens_DoDetachPort:6038: Detach and free port 0x600014c resources (interrupt) from ENS handle: 0x450307a99cc0

Environment

VMware vSphere ESXi

Cause

High host memory fragmentation can prevent VM vNICs from allocating contiguous physical memory after a vMotion. This leads to vNIC activation failure and the VM becoming unresponsive post migration.

Resolution

The issue has been resolved in ESXi version 8.0p06 (build-24859861).

In the below release notes, we can search for - "PR 3480453: Virtual machine vNIC fails to activate after a vSphere vMotion operation":

VMware ESXi 8.0 Update 3g Release Notes