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I have a VM that is unreachable every new day, because it got a new IP in a other subnet i believe (other subnet mask ie instead of What could be the cause of this. I'm running Hyper-V on Windows Server 2008 R2 SP1.

Things complicating this setup is that the router acts as a DNS and a DHCP and the server also acts as a DNS. All the workstations and servers are configured to choose the Server ( as the primary DNS.

What could be the reason for this problem?

IP numbers:

  • is the router
  • is the server
  • is the hyper-v host

network map

Below: The IP settings for the Hyper-V host and the VMs share the same except for the IP address. Hyper-V Host IP Settings

I wanted to post the question on serverfault but don't have the points for the picture.

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Does the Hyper-V get IP's from DHCP? – VBwhatnow Aug 10 '12 at 9:25
Yes it does. When its all going as planned the DNS (and DHCP?) is the Server with the AD. – Tim Aug 10 '12 at 14:34

You could have two DCHP servers running, or your DHCP server is slow in responding to renewal requests and the VM:s switch to APIPA addresses.

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