Virtual PC 2007 - Mac address issues

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Hey all. I teach an MCDST class at my local college and even though it's a single course, it's split into two sections (70-271 & 70-272).

In the firt part of the course (271) one of the early labs was for the students to install XP Pro and they did this onto brand new Dell PC's that had blank hard drives.

So before the second part of the course started I decided I would use VPC 2007 on the PC's they had built and had been using as this would allow them to carry on and do stuff on the host PC if they wanted to re-try 271 labs and also work on the 272 labs in a virtual machine.

So I set everything up, had a virtual server running at the front of the class and all the virtual workstations setup, one to each PC running inside VPC 2007. They needed internet access and also to be able to access my server and partner PC's, so the network adapters were bridged.

Because of the unusual nature of the way the Internet was provided to the room (ICS on the tutor PC) I ended up using static IP's on the first of two virtual NIC's in each VM, and the second virtual NIC was on auto-obtain. This seemed to work ok, but there was a lot of oddness with some VM's being able to ping their partner PC's and some not. Then the odd PC would not be able to ping the server ...

I was convinced that the physical NIC's in the Dell's weren't coping with having two virtual NIC's bridged across them, so I set just a single adapter on each VM, took the ICS PC out of the loop and used a proper server with RRAS and NAT configured on it, and also DHCP to sort things out.

When I initially tested this with just one PC and the server it worked perfectly. When everyone tried it last night, things went rapidly pear shaped. People were getting the same IP's from DHCP even though there was only a single lease showing on the server etc..

I then suddenly twigged that it could be the MAC addresses of the virtual adapters. So I got everyone to do an ipconfig /all and lo and behold, about 6 or so of the VM's had identical MAC addresses. At this point I ditched the VM's completely and got them to repeat the 272 exercises on the host PC's. I ended up wasting a lot of time until I figured this out. I never thought for a second it would be an issue.

The setup I used won't be that common, but if you have a couple of VM's on one PC and a couple on another both on the same network, then you could also have a problem with conflicting MAC addresses. I tested this in work this morning. Fired up 4 VM's on one PC and two on my laptop and straight away got two sets of conflicting addresses between the two hosts.

Doesn't seem to be an issue if you are running several VM's on a single instance of VPC though.

 

Erm, I 'may' (that means I did yes ) have copied all the VMC files yes. That would explain it, grr. All that hassle and I could have just re-created the VMC's.

I'm off for a cry now.

 

Not sure if this helps.

But I went to my mates who has 4 PCs for some reason and used VMware to link them together by copying the files, when they all went onto the network it froze and crashed because they all had the same MAC address.

So I binned Virtual PC on 3 of them and installed it on every computer and it worked, they could all talk perfectly together.

 

I had a similar issue recently where I was trying to add Virtual XP machines to a domain in VPC 2007. I had just copied the vhd files assuming it would be ok, but each pc had the same SID and only one of them could join the domain.

I ended up using Sysprep on one of the machines and then cloning the sysprep'd vhd file. Then when I need a new machine I just copy the sysprep'd vhd and run it as a new machine. The setup only takes a few minutes before the o/s is installed and then you're away!

 

Yeah I knew I would have to change the SSID values on each VM and I had already done that using newsid, but just didn't twig about the VMC's.

 

In VMWare Workstation I can copy virtual machine files, and when powering the new copy up VMWare tells me it has a non unique identifier, if this has been moved, keep it, if it has been copied create a new one, this refreshes machine unique info like MAC addresses (don't think it does the same with SIDs though)

Does VPC not have a similar option/command?

 

Well I didn't think so, but a quick googliser later and it seems you can modify the .vmc file directly.

If you open the vmc file in notepad you'll see it looks like an xml file.

Just remove the data from the <ethernet_card_address type="bytes"></ethernet_card_address> tag.

When you restart the machine VPC will generate a new MAC address for you.

 

Good to know, the thread turned out useful in the end.