Virtual PC, Shared Networking and the problems with Ping

Anyone who has spent time troubleshooting networking problems will be more than familiar with the tool – Ping. However – there are two problems with using ping with shared networking under Virtual PC:

  1. 192.168.131.254 does not respond to a ping.

    One of the first steps in network troubleshooting is to try and ping your gateway address.  Unfortunately, with Virtual PC and shared networking, the gateway address (192.168.131.254) does not respond to a ping.  This is completely benign behavior – as all other aspects of networking still work – however it has tripped up many people who were trying to diagnose network connectivity with shared networking.

  2. You can only ping external computers if you are running Virtual PC with an administrative user account.

    Virtual PC’s shared networking implementation is a simple NAT engine.  Virtual PC is responsible for sending and receiving network traffic for the virtual machine as a standard Windows user mode application.  For security reasons, only applications that are running as an administrative user are able to generate translated ICMP packets, such as the ones that are needed to support ping with shared networking.

    N.B. This means that if you are running on Vista and want to use ping inside a virtual machine with shared networking, you will need to manually launch Virtual PC ‘as administrator’.

Thankfully neither of these issues are show stopping problems, but are just interesting oddities.

Cheers,
Ben