Troubleshooting network connection issues caused by Proxy ARP

Products

• VMware vSphere ESXi

Issue/Introduction

Symptoms:

• Linux aliased interfaces lose network connectivity.
• Windows virtual machines lose network connectivity.
• Aliased sub-interface eth0:0 can be pinged only by eth0.
• A virtual machine cannot connect to network.
• A virtual machine cannot browse the workgroup.
  

Environment

VMware ESXi 3.5.x Embedded
VMware vSphere ESXi 5.0
VMware ESXi 4.0.x Installable
VMware vSphere ESXi 5.5
VMware ESX 4.0.x
VMware vSphere ESXi 5.1
VMware ESX Server 3.5.x
VMware ESXi 4.1.x Embedded
VMware ESXi 4.1.x Installable
VMware ESXi 3.5.x Installable
VMware ESX 4.1.x
VMware ESX Server 3.0.x
VMware ESXi 4.0.x Embedded

Cause

Network connection issues may occur if you have Proxy ARP enabled. For more information, see Cisco's IP Addressing Services documentation on Proxy ARP.

Note: Proxy ARP must be used on a network where IP hosts are not configured with a default gateway and do not have any routing intelligence.

Resolution

To resolve this issue, you must disable Proxy ARP on switches, firewalls, and routers.

For more information, see Cisco's IP Addressing Services documentation on Proxy ARP.

Note: A good way to determine this is to find a virtual machine on the same vSwitch, and run arp -a. If there are no entries for the virtual machine experiencing the issue, make sure it is disconnected from the network, and then attempt to ping it. On Cisco Routers the Proxy ARP is enabled by default. But if HSRP (Host Standby Router Protocol) is enabled on the router then Proxy ARP is disabled automatically. Make sure you verify the settings for both on the Cisco Router and follow the vendor's guideline for desired configuration.

You should not receive any responses however if you run arp -a once more, you may see the IP address show up in the list with a MAC address (not necessarily the MAC address of the virtual machine). This means there is a device on the network that is responding on behalf of the machines, based off learned MAC addresses (Proxy Arp).

Note: The preceding link was correct as of June 25, 2011. If you find that the link is broken, provide feedback and a VMware employee will update the link.

Additional Information

Each Operating System handles this issue differently.Proxy ARP が原因のネットワーク接続問題のトラブルシューティング