Troubleshooting duplicate Mac or IP addresses in VMware vCenter Server

Products

• VMware Cloud Foundation
• VMware vCenter Server
• VMware vSphere ESXi

Issue/Introduction

Symptoms:

• Execution of vMotion on the host fails intermittently and randomly.
• Host becomes unresponsive.
• In the /var/log/vmkernel.log file, you see entries:
  
  arp: xx:xx:xx:xx:xx:xx is using my IP address xx.xxx.xx.xxx on vmk1!
  arp: xx:xx:xx:xx:xx:xx is using my IP address xx.xxx.xx.xxx on vmk1!
  arp: xx:xx:xx:xx:xx:xx is using my IP address xx.xxx.xx.xxx on vmk1!

Cause

This issue occurs when the same IP address is assigned to the management network port on two different hosts.

Resolution

To resolve this issue, identify the host whose IP address is the same as the host which is affected and change the IP address of the conflicting host.

To change the IP address of the conflicting host:

1. Open VMware PowerCLI.
2. Run this command to connect to VMware vCenter Server:
   
   C:\PS>Connect-VIServer -Server vCenter_host_name -User admin -Password pass
   
   where:
    
   • vCenter_host_name is the hostname of the vCenter Server
   • admin is the Administrator login
   • pass is the password for the Administrator account.
      
3. Run this command to create a spreadsheet file containing the list of management interfaces vCenter Server is aware of.
   
   C:\PS> Get-VMHostNetworkAdapter | select VMhost, Name, IP, SubnetMask, Mac, PortGroupName, vMotionEnabled, mtu | Export-Csv C:\HostNWDetails.csv
   
   Note: This command may take some time to complete.
4. Open the C:\HostNWDetails.csv file and locate the IP address duplicates in Microsoft Excel.
5. After identifying the duplicate IP address, change the IP address using vSphere Client or vSphere Web Client.

Additional Information

Troubleshoot duplicate IP without shutting down known device