Networking with VM Hardware Version 7

For virtual machines that are used in VMware Infrastructure 3, there is some amount of intervention required to get the machine to work with all of the features of vSphere. Ironically, VI3 virtual machines carry the designation version 4. vSphere virtual machines are at version 7.

For a virtual machine to be upgraded to version 7, the upgrade virtual hardware task needs to be completed on the virtual machine while it is powered off. This is quick and easy, but is only the entry point to all of the new vSphere features such as thin-provisioned VMDKs and using the VMXNET3 network adapter. When you do this, it is important to note that a few things may happen to the virtual machine. Here is a list of recommendations to go about upgrading the virtual machine hardware in regards to the networking configuration:

Install VMware Tools first. A virtual machine at version 4 can have the vSphere VMware Tools installed before the actual upgrade. This will allow all of the components to be natively visible within the guest operating system.

Document IP addresses before update. This sounds silly, but when the VMXNET3 network adapter type is used, the previous connections are removed because Windows guests see that as a different type, and the IP configuration is retained with the previous adapters. If you need to retrieve your IP addresses from the configuration on the other adapters (namely the flexible type from VI3), you can check this area of the Windows registry: HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services. There you will see each interface, both currently installed and non-present. In the \Parameters\Tcpip section you can find the IP address configuration that was used on the previous adapters.

Remove non-present devices. Taking a page from good P2V practices, it is a good idea to clean up the obsolete devices that are not present in the virtual machine. For Windows systems, you can remove the non-present devices by running this command at a command prompt:

1. Run cmd.exe
2. Type: set devmgr_show_nonpresent_devices=1
3. Type: devmgmt.msc
4. Select "Show Hidden Devices" from the View menu.
5. Look in the network adapters section and remove the pieces that are not present anymore on the virtual machine, whether these are physical interfaces or VI3 components.

Make sure MAC addresses aren't going to be an issue. If you change to VMXNET3, your address space for MAC addresses is changed from the previous range for VI3 interfaces using the flexible adapter type. Here are some tricks on managing custom MAC addresses that I blooged about last week.

Make no mistake, there are hurdles to cross and this is just the networking category. But it doesn't make much sense if there is a mix of version 4 and 7 virtual machines in a vSphere environment.

Have you learned any networking lessons when upgrading from version 4 to version 7? Share your comments here.

Posted by Rick Vanover on 04/29/2010 at 12:47 PM