VMs in the same subnet hosted on different ESXi hosts are unable to communicate with each other

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VMs in the same subnet hosted on different ESXi hosts are unable to communicate with each other

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Article ID: 417824

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Updated On:

Products

VMware vCenter Server

Issue/Introduction

VMs in the same subnet and VLAN hosted on different ESXi hosts are unable to ping each other.
Initiate the pings from source VM to destination VM and the pings do not go through:

Environment

VMware vCenter Server
VMware ESXi

Cause

In the packet captures performed on the uplinks used by source and destination VM, it is observed that while pinging the destination VM from source VM, the ARP requests are leaving the source vm's host uplink but no ARP requests are coming on the uplink of destination VM's host.
Below command can be used to perform packet captures on the uplink of the ESXi hosts used by the source and destination VMs:
- pktcap-uw --uplink vmnicx --capture UplinkSndKernel,UplinkRcvKernel -o - | tcpdump-uw -r - -enn
Replace vmnicx with the appropriate uplink interface used by VM. To find the vmnic, please refer to How to find which vmnic a VM is using on ESXi
For detailed steps on performing packet captures, refer to Packet capture on ESXi using the pktcap-uw tool.

Resolution

Since the packet drop is identified as occurring outside the ESXi hosts on the physical network, the issue must be resolved by the physical network team.

Engage the physical network team.
Request the team to check the physical network configuration (e.g., VLAN settings, switch port configuration, spanning tree) relevant to the two ESXi hosts' uplinks.
Instruct the team to trace the packets in the physical network infrastructure to precisely identify the drop point and correct the misconfiguration.

Additional Information

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