So I had a power outage yesterday and it was longer than my UPS's battery (over an hour).

Anyhow, the hyper v server power went out. After the power outage I booted it up, but the networking (external) on any of the nics does not work anymore. I have 3 nics in it, one for the host and one each for 2 vm's. I should say networking does not work over the nics anymore. Cant ping to the server from outside, nor ping from the server.

If I go into sconfig it shows the hosts nic, as usual, plus a test internal network nic I had not yet removed. using coreconfig I can see those nics as well, they show enabled and connected. Also the switch I plug into shows that they are connected (lights on, 1 Gbit connection) All networking parameters are as they should be (ip, subnet, etc)

Using core config VM section, both vm's are up and running.

I have tried restarting, powerting off completely and restarting, enebling/disbaling the nic, plugging into different switch ports, tried a different switch. All my other servers are running fine, including two vm servers, so its unlikely external to the server.

At this point I really have no idea what to try next. I dont have any spare nics to go try, but I doubt its NIC's considering all 3 are not functional (or better to say the network is not running over any of the 3 nics)

Any suggestions as to some things I can try?


  • You've verified the Networking settings in a Hyper-V Management Console? – Chris S Aug 28 '12 at 14:33
  • Does the host have network access? – Joel Coel Aug 28 '12 at 14:34
  • Chris, since I can't connect to the server, no – mattlant Aug 28 '12 at 14:59
  • Joel, no the host cannot access the network, but network settings are correct, verified with ipconfig all. I tried changing settings and back again, no change – mattlant Aug 28 '12 at 15:01
  • Were you aware of the power outage? – joeqwerty Aug 28 '12 at 15:07

Did you have any other equipment reboot due to the power outage? It almost sounds like there were VLAN tagging settings required for connectivity on a network switch that were lost because no one wrote the running-config to memory.

First make sure that you can access the Hyper-V host. You need to verify that your management interface hasn't been accidentally set to an Internal or Private interface in Hyper-V's Virtual Network Manager. Once you who have successfully verified that you have connectivity to the host you can move on to the VMs.

Verify that your two NICs that are designated for use by your VMs are "External Connections" in Hyper-V's Virtual Network Manager. Make sure the checkbox "Allow management operating system to share this adapter" is also enabled. You should now be able to ping or connect to the IP address for both of these NICs. Then confirm that Virtual Network or Virtual Interface you are connecting to each NIC is added to the appropriate VMs.

  • Thats where 1 of the problem lies. It's hyper v server (core) and I cannot connect to the host. Yes I had 2 other hyper v servers go out but they do not have any problems. I didnt have any vlans setup. I have distinct physical subnets on my network rather than vlans. – mattlant Aug 30 '12 at 16:34
  • Did you verify that whatever interface you are using for management of the Hyper-V host is not being used as an Internal or Private interface? – user62491 Aug 30 '12 at 17:25

I'd just start your network config over from scratch. Verify any vlan settings you might have setup. Reload drivers, re-setup your hyper-v networks. Reset your client vms to the new networks.

  • No vlans, But yes I agree I am at a point where I may go about this, at least at a low level, as I cannot connect to the host with a management interface. Unless anyone knows of a powershell management interface where I can manage the networks. – mattlant Aug 30 '12 at 16:36
  • Just a note, I always make sure that whenever I've loaded a system running Core or Hyper-V server that I've got a way to manage all of the particulars of the local environment from that machine. For hyper-V I load up a Windows7 VM with the RSAT packages loaded and configured if I'm not running a windows 2008 VM on the machine. – ErnieTheGeek Aug 30 '12 at 18:41
  • On that note, what VMs are you running? If any of them are server 2008 r2 you might be able to manage your hypervisor from there. – ErnieTheGeek Aug 30 '12 at 18:41
  • so I have a hyper v core server, the free version, sp1. I am able to communicate with 1 of the servers on it, as noted above I though they all were on seperate nics, but one of the servers shares a virtual nic with the host. That is good news that networking is at least working within the host. I like the thoughts you have above, but is there any way to use remote desktop from within the hyper v host? – mattlant Aug 31 '12 at 20:31
  • Sort of, you need to kind of hack it in. I can't find my notes on it right now, but essentially you need to find an xp workstation with the original rdp client and move the corresponding rdp files over to your hyper-v host. After that you'll be able to manually launch the rdp client. – ErnieTheGeek Sep 4 '12 at 15:13

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.