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So I've got Hyper V running on windows 8.1. I configured an external virtual switch which uses my wifi physical card. So I get a virtual adapter that gets its ip from my dhcp server (e3000 router). When no VM are running, I can see my host's name in the router's dhcp client table along with its mac address. So far so good.

When I start a VM, I no longer see my host in the router's dhcp client table, instead I see my VM's name with its own IP address but with the same mac address that the entry with my host's name used to show, instead of the mac address of the VM's virtual adapter (dynamically assigned, but I can see it on the networking tab of the hyper v manager). This looks weird to me, but still, everything works fine, my host still has an IP but its not showing in the router's dhcp client table.

Then, after some time, my VM reports that there is an IP address conflict as it starts trying to use my host IP address. I get entries in the windows event log reporting that the dhcp-client got an ip (my host's IP) for mac address xxxx (my VM's virtual adapter mac address) but that this IP is already in use by (my host's mac address). And the same event with the same data repeats over and over. My VM is running windows server 2008 SP2 and is a domain controller, but I use to run the same setup without problems. I recently ran a series of windows updates on my VM since it hadn't run in a long time. This setup used to work without ip address conflicts before.

Any idea what's going on? Thanks!

1 Answer 1

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There seems to be an issue binding an external virtual switch to a wireless physical adapter. The whole issue is described here.

To make a long story short, the solution is to assign a static IP to the VM's virtual adapter. If you happen to connect your wifi adapter to a network with another subnet range, you have to edit your VM's IP address.

update:

An even better solution. Replace the external virtual switch by an internal virtual switch. Activate the "Routing and remote access" service (Automatic delayed start). Activate connection sharing on your physical wifi card with the vEthernet virtual adapter (on your host). Start your VM, it should automatically pick up an IP from the dhcp service provided by connection sharing. If not, set one up manually in the same subnet as the virtual adapter on the host and set the gateway and dns to be the virtual adapter on your host. By default the virtual adapter on your host will have ip 192.168.137.1. This way, no matter what ip your physical nic gets, your VMs keep the same IP and are on their own network with the virtual adapter on the host + they all have internet access (if your physical nic has internet access).

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