ESXi hosts' VMkernel adapters are unreachable from their peer hosts

Products

• VMware vSphere ESXi

Issue/Introduction

Unable to ping certain ESXi hosts' VMkernel adapters from other hosts within the same cluster and subnet.

Environment

VMware ESXi

VMware vCenter Server

Cause

The connectivity failure is due to the incorrect MAC entry in the  ARP cache of the physical switch. Physical switch is replying to the ARP request with an invalid MAC.

When a ping is initiated from the source Esxi host vmkernel to the destination Esxi vmkernel, the arp reply is coming from the physical switch instead of the destination vmkernel  and the MAC address of the ARP reply packet is an invalid MAC.

Resolution

This is an issue with the physical switch. 

For troubleshooting use the commands in KB Packet capture on ESXi using the pktcap-uw tool to take the packet captures  and check the source and destination.