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We have a strange problem with an interaction between our Hyper-V virtual host and the hosted virtual servers. Both virtual hosts and virtual servers are running Windows Server 2008.

When a virtual server is added to a MS NLB instance, the entire virtual host panics and shuts down. The MS NLB is configured in unicast mode, so each node shares a common MAC address. From what our sys admins can tell, the virtual hosts panic when the MAC address of the virtual network devices is changed by MS NLB.

I think a MAC address conflict within the virtual host is causing the problem - six virtual nodes in the NLB cluster are hosted on only two physical hosts. (I know this makes no sense. I didn't do it.)

Has anybody ever heard of this problem and how do you recommend solving it?

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I'm a little're using network load balancing on virtual systems within the same physical host? How does that add redundancy or load balancing since it's going into the same physical hardware in the end? – Bart Silverstrim Oct 6 '09 at 13:14
Yes we are - and you are correct. It adds nothing. The systems administrators I deal with aren't always the brightest of bulbs. – Ryan Michela Oct 7 '09 at 1:14
up vote 0 down vote accepted

I was just ran into an answer to this problem if you are still looking.

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