Bridge not working in QEMU virsh

Question

I have two production systems that are down. I did not set them up, and am new to QEMU and virsh. While there are two, I am really only concerned with the one server called sbs2011, since that is the most critical, and when that is fixed, then the fix for the other will be evident. As you might have guessed, it is running Windows Small Business Server 2011.

Here is the situation: VMs are both running, the bridge seems to be up and working, but we cannot access the server. virsh net-list --all shows no networks. (Not sure if it is supposed to with bridging).

brctl show output:

bridge name     bridge id               STP enabled     interfaces
br0             8000.90b11c45aab6       no              bond0
                                                        vnet0
                                                        vnet1

Network Portion of Server XML file:

<interface type='bridge'>
      <mac address='de:ad:be:ef:01:01'/>
      <source bridge='br0'/>
      <model type='virtio'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x0'/>
</interface>

I have spent several hours working on this to no avail. I am thinking that perhaps the dnsmasq is not working correctly, but when I go to /etc/dnsmasq.conf, there are no uncommented lines in the whole file. I am looking now to see how the IP address would be set.

EDIT: OK, I don't think it is dnsmasq, since the server is Windows and it has a static IP address to itself. It is almost as if there is a routing issue.

EDIT: Well, the Windows 8 machine came up. Something tells me I might be the victim of a chkdisk or something. So, the answer to the question about virsh net-list showing networks is no, if it is using the host bridge.

Answer 1

OK. So, here is what happened.

The bridge was setup correctly, and, as suspected, when using a bridge configured on the host, it will not show up in virsh net-list at all.

What had happened was that the Windows server had become corrupt and was sitting on a restore screen, which we could not particularly use without reloading the entire server and reinstalling software, etc.

So, I shutdown the VM, renamed the disc image file, copied one from the previous backup to where the renamed one had been. Then I brought the server backup and it worked fine.

Important lesson: Always have a good DR backup!