How to enable virt-manager to create and manage virtual machines without a real network connection?

OS: openSUSE 12.2
Virtualization: QEMU-KVM

Issue:
Can connect to virtual machines using virt-manager only when a real physical network connection exists, even if the connection only has to be between Host and Guess running on the same machine.

Desired:
Manage, Connect to Guest without a real network connection

Error:
The error returned when no real network connection exists suggests that virt-manager absolutely requires VNC to establish a network connection between Host and Guest. Note that this error does not exist when a real network connection exists.

Internal error process exited while connecting to monitor: getaddrinfo(127.0.0.1,5900): Name or service not known

Possible solutions?

  1. Disable network “auto-sense” for connectivity, enabling “always on.” This is the approach used on Windows boxes. If this is an option, how?

  2. Enable a “Host Only” private network which is not bridged to real network devices. When I first built this VM, of course I selected the option to create a virtual bridge but if I had chosen not to bridge, would I have the desired result but if that would be the case, how would i configure “sometimes” Internet connectivity, perhaps configuring my Host as a Proxy Gateway?

TIA,
TSU

Minor update:
I’ve found that I can indeed create an “isolated network” that enables virt-manager to manage and start an existing VM without an active physical network connection.

Will continue to explore whether a network can be specified when a VM boots switching between an isolated and regular bridged networking.

BTW- I find it interesting that “bridged” networking implements NAT so the Guest VM has a private address behind the Host instead of an address on the same network as the Host’s real network.

TSU

Another minor update.
Instead of relying on a default but un-named virtual network created automatically when you setup virt-manager,

I’ve created isolated and forwarding networks. Both work excellently when I configure either to be available “on bootup,” but so far using virt-manager I’m only able to select the Host’s network configuration, not the client. Bottom line for now is that I can’t have both networks available at the same time and all clients have to use the same network.

I suspect with further investigation it should be able to configure network selection on the client using CLI instead of GUI.

Of course, if anyone else has tread down this path before, I welcome comment.

TSU

Updating:
What I thought was happening is apparently only partially true.

KVM supports two types of networking

User Mode Networking = Installed and available by default in KVM installations. A tell-tale on my system is that it’s automatically configured with a Class A Private Address space (10.x.y.z) with a Class C subnetmask (/24, aka 255.255.255.0).

Bridged Networking - Configurable but not available by default. The Guest should be visible on the network, not NAT behind the Host.

There is also another type of networking that can be configured an “isolated network” which I’ve been exploring. I believe that an “isolated network” may be a virtual network only on the Host which wnot support forwarding to other Hosts not deployed on the same machine. Note that this is different than User Mode Networking which does support forwarding.

Am currently investigating why some types of options are automatically available in some of my Guest VMs but unavailable in others. My early testing suggests that if you want to force User Mode Networking for openSUSE guests, you have to be certain no bridged virtual networks are available. But, to avoid another possible bug, if in the beginning you see an error something like “service unavailable: port 5900” you may have to at least temporarily configure an isolated network before optionally removing.

Note that so far I’ve found that once a machine has been configured for User Mode Networking, the GUI does not permit switching to another type of networking and vice versa.

TSU