Comment 6 for bug 520386

It is indeed a pain. I'd like to see this get fixed eventually. Even the upstream patch that's around somewhere that allows you to simply manually specifiy a bridge would be pretty good.

It's not *impossible* to use libvirt/KVM in these conditions, incidentally, it's just that after defining a new domain you need to manually alter the domain's configuration:

virsh qemu+ssh://<email address hidden>/system edit <domainname> (edit as appropriate), and then to change the default NAT network to bridge simply replace <interface type='network'> with type='bridge' and <source network='default'/> with <source bridge='br0'/>

Not ideal, but not that hard either.