ESXi Host "Not Responding" due to Management Network disconnect

Products

• VMware vSphere ESXi

Issue/Introduction

• Host shows "Not Responding" in vCenter. Total loss of connectivity and the host is unreachable via ping.
• Virtual machines running on the host lose network connectivity.
• The host may automatically recover after several minutes, only to flap back to a disconnected state later.
• During the failure, the host cannot ping its default gateway or other hosts within the same cluster.
• When the issue is active, from the DCUI console esxtop network stats show unusual amount of traffic passing through vmk0(management vmkernel adapter)
  
  
  
  
• A packet capture on the active physical uplink revealed a high volume of traffic originating from storage related IP address.
• Management network and virtual machines are placed on the same virtual switch and use a single active uplink.

Environment

VMware vSphere ESXi 7.x, 8.x

Cause

This issue occurs when the vmnic associated with the management network (typically vmk0) is in a "down" state. This can also be caused by network saturation, physical cable issues, or the link failing to initialize after a power cycle.

Resolution

To restore management access, verify and reset the physical NIC link state:

1. Log in to the ESXi host via the physical console or out-of-band management (ILO/iDRAC).
   
   
2. Navigate to the Troubleshooting Options and enable ESXi Shell if not already active.
   
   
3. Press Alt+F1 to access the command line.
   
   
4. Run the following command to check the status of the network interfaces: esxcli network nic list
   
   
5. Locate the vmnic assigned to the management network and verify if the Link status is "Down".
   
   
6. If the link is down, administratively bring the NIC up using: esxcli network nic up -n vmnic# (Replace # with the specific NIC number, e.g., vmnic4) .
   
   
7. Verify the host reconnects to vCenter automatically. If the host is still unresponsive, you must clear the network bottleneck by rebooting the host to regain management access.