For what it’s worth, if you’re removing Hyper-V and adding it back in, that is probably curing whatever causes the MAC duplication in your environment, although I would anticipate that removing and adding the external network (which claims a host NIC) would be sufficient. That’s pretty much the differences between our approaches.

1. Remove the virtual networks in Hyper-V
2. Uninstall the Host network adapters
3. Remove the Hyper-V role (auto-restart x2)
4. Install Hyper-V role (auto restart x2)
5. Verify Host network adapters re-installed during restart
6. Disable unnecessary PCI NIC (I have two NIC’s, only need one for this environment)
7. Create needed virtual networks
8. Set network adapter in each VM to appropriate network

Interesting note, I used to set up this class on a disk that had an XP partition on it as well. Due to XP’s different boot files vs. those now used for Vista, 7, and Server 2008, back then I was forced to perform ‘post-imaging’ a start-up repair on the partitions which used bcd (Vista, 7, 2008). I also had to remove and re-install the Hyper-V role so it’s virtual BIOS was set-up correctly. These were both disrupted due to the imaging process with Symantec Ghost. I think that repair was also resolving the issue we are discussing here without me knowing it because I was forced to do it for these other reasons. So I would say yes, this is all related to the imaging process.

I don’t even recognize the MAC address 00-21-9B-6E-8D-79. The host MAC address is 00-23-AE-91-90-D7, not even the same OUI. The Dynamic MAC address pool for Hyper-V is 00-15-5D-1C-32-00 to 00-15-5D-1C-32-FF.

I’m having this problem on Windows Server 2008 R2 with Hyper-V as the only enabled role. I’m in a classroom with 21 computers which were all disk imaged via Ghostcast so the VM’s MAC addresses are identical but I don’t understand, when the VM’s are turned off, how this could cause a problem with the Host machine’s network.

I do believe though that it has something to do with duplication because with just one computer turned on, the internet speed is fine and the only symptom is that it won’t ping the default gateway. However as more machines are turned on the network performance gets worse.

I had a Network Technician over here earlier to confirm everythign was configured properly and functional on the switch. I have this classroom set up for Microsoft 6420B Fundamentals of Windows Server 2008 and my previous semesters’ configurations have not had this problem. The only difference between previous set-ups and this set-up is that I had an XP partition on the disk in previous set-ups, now it’s just two partitions of 7 x64, one of Vista x64, and the partition of Server 2008 R2 in question here. The previous arrangement with XP did require a post-imaging start-up repair and Hyper-V removal and re-installation and the NIC’s on the VM’s to all be set again to ‘Private Network’. But I’ve tried all that again and still no change.

Any help would be greatly appreciated.

Yeah, I believe that is the case with P2V, but so you know this is an issue with Hyper-V hosts, not the virtualised guest.

Cheers,

Tristan