[libvirt-users] Problems with VM networking on Ubuntu Quantal

I have shifted some VM's to a new server running Quantal and have had a world of trouble. The first one was caused by issues with an apparently compiled in path in their apparmor version which forced VM pools to be in /srv or similar rather than where I wanted them. For now this was not a big issue, and thankfully the server where it would be a big time problem (there are individual drives per major customer or user) is Debian. But... I still have issues. The networking has changed considerably and although I can get my VM running, I cannot reach it. The new quantal machines give you something like this: br0 Link encap:Ethernet HWaddr **** inet addr:10.0.0.xx Bcast:10.0.0.255 Mask:255.255.255.0 inet6 addr: *****/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.0.0.0 inet6 addr: ::1/128 Scope:Host UP LOOPBACK RUNNING MTU:16436 Metric:1 p6p1 Link encap:Ethernet HWaddr **** UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 virbr0 Link encap:Ethernet HWaddr **** inet addr:192.168.122.1 Bcast:192.168.122.255 Mask:255.255.255.0 UP BROADCAST MULTICAST MTU:1500 Metric:1 vnet0 Link encap:Ethernet HWaddr fe:54:00:84:3c:4f inet6 addr: fe80::fc54:ff:fe84:3c4f/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 The VM machine has a static ip on the same network, ie 10.0.0.x. It worked fine on the old server but is not reachable (and cannot connect outward). Forwarding is turned on: cat /proc/sys/net/ipv4/ip_forward 1 The VM has eth0 Link encap:Ethernet HWaddr **** inet addr:10.0.0.xx Bcast:10.0.0.255 Mask:255.255.255.0 inet6 addr: *****/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.0.0.0 inet6 addr: ::1/128 Scope:Host UP LOOPBACK RUNNING MTU:16436 Metric:1 An attempt to ping from the VM to anything outside gives a "Destination host unreachable" message. It has been a long time since I set the old machine up, so I may well have forgotten some step.