Some virtual machines unable to connect to network and internet from Server 2008 R2 w/Hyper V

virtual machines are not able to connect to network or internet today but were able to just last week.  this does not apply to all of the virtual machines, one continues to connect out
dmaxITAsked:
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dmaxITConnect With a Mentor Author Commented:
OK, got to the root of the issue -- The host machine is in a very small segment that has been configured for distribution via DHCP.  If the machine owner shuts down a running virtual machine and brings up a different one, it will connect out successfully.  If she powers up another virutal machine at the same time, it will not connect out. She can power off the working one and the 2nd one will now connect out.  The IP range is not one I really want to allow DHCP for - not sure why this small group was allowed in the first place, but it's there.  Anyway, I have some direction to look at for a long-term resolution, but some decisions to be made .....  Thanks for all your ideas and suggestions
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Geek_NabilCommented:
Did you recently update or modify your Hyper-V? Any ISA Servers in the network, check the configuration, it might be blocking access.

What are the guest OS's running on the Hyper-V?
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dmaxITAuthor Commented:
Not sure what may have changed - there are 2 users with access and creating guests - I think someone did something, but I cannot see any difference in network setup between guests.  There are no ISA servers to contend with.  The guest machine(s) are XP SP3.  Thanks for any ideas
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Geek_NabilCommented:
Check any recent Service Pack Installation, Check the guest tools are installed and up-to-date (try reinstalling the guest tools), Check the Host Firewall Configuration, try disabling it and test.
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dmaxITAuthor Commented:
no recent SP installs on either Host or Guest.  Guest Services reinstalled. No firewall enabled.  
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Geek_NabilCommented:
I want you to check the MAC address of every machine and tell me if they are the same.
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dmaxITAuthor Commented:
owner of project machine reports that none of the virtual machines have the same MAC
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Geek_NabilCommented:
Remove the Virtual Network Adapter while the guest OS is running, and add it again, also if you are using a bridged connection on the Virtual Network Adapter, check your network switch configuration, perhaps there is a limit on the number of MAC addresses per Network Port.

Also Try using a Host only network connection on the Virtual Network Adapter, if the problem is solved in the guest OS, you should check your network set-up.
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dmaxITAuthor Commented:
we have determined we can create a new XP virtual machine from "scratch" and it will connect to the network and beyond without any problem - any new virtual machine created from an existing machine "template" will not be able to connect -- the owner of the machine contends this was not an issue up until this week.
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Geek_NabilCommented:
So the problem is not in the hyper-V or network, it is in the virtual os,
do you have any backups or snapshots of the virtual machine, when things worked.
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Geek_NabilCommented:
Glad i could helo you realise your problem.
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