Intermittent vCenter connectivity loss due to duplicate IP address in the environment
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Intermittent vCenter connectivity loss due to duplicate IP address in the environment

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Article ID: 422967

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Updated On:

Products

VMware vSphere ESXi VMware vCenter Server

Issue/Introduction

  • vCenter may experience intermittent connectivity loss, including an inability to connect via SSH (for example, using PuTTY) or the web client.
  • From the vCenter console, pinging the gateway IP address fails. However, other virtual machines residing on the exact same ESXi host continue to function normally with no network interruption.

Cause

This issue is caused by an IP address conflict. Another device or virtual machine on the network is configured with the identical IP address as the vCenter Server. This conflict creates a duplicate entry for the MAC address in the ARP table, causing network traffic intended for the vCenter Server to be intermittently misrouted.

Resolution

To resolve this issue, identify and reconfigure the device or virtual machine that is incorrectly using the vCenter's IP address:

Step 1: Identify the Conflicting MAC Address

      1. Log in via SSH to the ESXi host where the vCenter Server resides.

      2. Run the following command to view the host's ARP table

        esxcli network ip neighbor list

      3. Locate the vCenter Server's IP address in the output. If the IP address is mapped to a MAC address that does not belong to the vCenter VM, note the "VM name/device" MAC address.

Step 2: Locate the device which is using duplicate MAC

      1. Search the vSphere inventory for a Virtual Machine using the rogue MAC address identified in Step 1.

      2. Note: If the MAC address does not belong to a VM in the inventory, Engage the network team to trace the MAC address on the physical switch ports.

Step 3: Resolve the IP Conflict

      1. Once the conflicting device is located.

      2. Reconfigure the device's network settings to use a unique, available IP address (or switch it to DHCP).

      3. Alternatively, if the VM was deployed in error, gracefully shut it down or disconnect its virtual network adapter.

Step 4: Validate Network Stability

      1. Clear the ARP cache on the ESXi host or wait a few moments for the network to automatically flush the stale entry.

      2. Perform a continuous ping to the vCenter Server IP address.

      3. Verify that the replies are consistent and that the vCenter UI loads without intermittent disconnects.

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