Virtual Machines Sporadically Lose Network Connectivity on a Particular ESXi Host

Products

• VMware vSphere ESXi

Issue/Introduction

• Virtual Machines become unreachable sporadically on one or some ESXi hosts, but not all hosts in the cluster. 
• Only one or some VLANs, but not all VLANs are affected.

Environment

VMware vSphere ESXi

Cause

This behavior indicates that there is a VLAN missing from the trunk configuration on the upstream physical switch ports.

Resolution

Engage your internal network team to have the affected VLAN(s) added to the trunk configuration on the relevant physical switch ports. 

Additional Information

To find the relevant ports on the upstream physical switch, CDP/LLDP may help to identify the correct switch ports: 

• In vSphere, select an affected host > Configure > Networking > Physical Adapters > Select a vmnic > Select the CDP or LLDP tab to see information about the neighboring device. 

VLAN configuration on virtual switches, physical switches, and virtual machines