Network freezes with KVM/libvirt and ip_forward = 1
Yes, I solved it by changing the bridge setup. Previously, I added the bridge directly to eth0 with the external IP address. I changed this to an internal bridge with the IP 10.0.0.1 and now route the public VM IPs through this bridge.
what are the first 2 characters of your MAC address? There is a known issue with brctl, where the MACs start off too high (e.g. new HP NICs start with D8:...)