During an OWSUG user group meeting a few weeks ago, a member approached Garth and I with an issue in Hyper-V.
He was not able to connect to a VM using the network no matter what he tried. My first instinct is always to verify the IP connectivity with ping tests and so forth.
The configuration was confirmed to be fine in Hyper-V in that, he was using an external network so binding to the physical NIC.
The member kept repeating that this was after a P2V conversion and something did not sit right.
The solution was eventually discovered by Garth. I’ll post this as a caution to hopefully save other ITPros time and be aware of this potential issue.
Remember what you are actually doing with a P2V conversion. You are virtualizing a physical host computer. It does not have to be a host in the VM sense…
Elements of the VM will be identical to the physical system (IP address, server name, MAC address, so on)…
The reason this is important is that you cannot keep BOTH systems online at the same time without making some changes…
The element in particular that I want to point out is the MAC address. After P2V, this is set to static and it retains the same value of the MAC address from the physical system.
You cannot have 2 systems on the network at the same time with identical MAC addresses just like you cannot have 2 systems on the network at the same time with identical DNS names, NetBIOS names, or IP addresses.
Duplicate MAC addresses are way more rare of an issue because of some of the safeguards in place by the standards committees who make the network cards.
P2V actually does this on purpose…
The idea being that the physical system is usually migrated for purpose of being decommissioned or repurposed. Bringing it back online at the same time as the VM you made from P2V creates this duplication conflict.
There is another issue which was not covered that I will go into now. Duplicate SIDs…
If you P2V a system that is a member of an existing AD and keep both systems around, 1 SID must change.
Microsoft does not support changing SIDs after a machine has been joined to an AD domain.
There is a utility available from winternals called newsid. This does the job and honestly, I have deployed an army of over 30 systems imaged with ghost and ran newsid after the fact with no issues. A reboot is required after running the tool.
Remember, use this tool at your own risk… :-)
Read the complete post at http://owsug.ca/blogs/brad/archive/2009/04/24/Unable-to-connect-to-Hyper_2D00_V-VM-after-P2V-conversion.aspx