Virtual machine network failure due to duplicate IP addresses

Products

• VMware vSphere ESXi

Issue/Introduction

Symptoms:

• You cannot bring up up networking for ESX or virtual machines
• Virtual machines cannot connect to the network
• Virtual machines indicate that there is a duplicate IP address on the network

Environment

VMware ESX Server 3.0.x
VMware ESX Server 3.5.x
VMware ESX 4.0.x
VMware ESX Server 2.5.x

Resolution

Duplicate IP addresses on the network may cause virtual machine network failures.

To check for duplicate IP addresses:

1. Disable the virtual machine or ESX interface.
2. Ping the IP address to see if the IP responds.
3. Check arp from another box.
4. From Windows, ping the target IP address with the command:
   
   c:\ ping x.x.x.x
   
   
5. Run the command:
   
   c:\ arp -a
   
   The output appears similar to:
   
   Interface: IP_Address --- 0x4
   Internet Address Physical Address Type
   IP_Address MAC_address dynamic
   IP_Address1 MAC_address1 dynamic
   IP_Address2 MAC_address2 dynamic
   
   Check the arp list of MACs to locate the device that has the conflicted MAC address.
   
   
6. From ESX or Linux, run the following command:
   
   arping -I vswif0(eth0) x.x.x.x
   
   The device in conflict reports its MAC address.
   
   
7. SSH or Telnet can reveal information about the duplicate IP address. From ESX or Linux, run the following commands:
   
   ssh x.x.x.x
   telnet x.x.x.x
   
8. From Windows run the following command:
   
   c:\telnet x.x.x.x 22 (Checks to see if the firewall is blocking port 22)
   c:\telnet x.x.x.x
   c:\ net view \\x.x.x.x

If you determine that there are duplicate IP addresses, see Resolving virtual machine IP address conflicts issues (1008177) and Verifying gateway IP connection using the tcpdump command (1008017) for further troubleshooting information.