Ross S. W. Walker wrote on Tue, 1 Apr 2008 11:14:58 -0400:
Yeah, I would use xenbr0 (or eth0 in 3.2 parlance) as the bridge if you plan on using an external DHCP server and avoid the whole NAT and dnsmasq mess. I would probably use virbr0 as a nice virtual network only service, remove forwarding and NAT on it and keep it for internal traffic only.
virbr0 ist just there when libvirtd gets started, it's useless as it is not bridged to anything anymore. However, I'm not able to reproduce my last results consistently. As expected once I rebooted the problem was back and now I can start libvirtd, kill dnsmasq and still get no IP address. I also found a posting on xen-users that describes exactly my problem and solution http://lists.xensource.com/archives/html/xen-users/2007-08/msg00716.html
and the solution is in that direction I suspected. I tried that and again it doesn't work consistently for me. If I do "iptables -A FORWARD -s 0.0.0.0 -d 0.0.0.0 -j ACCEPT" it seemed to work first, but then stopped working as well. I now get an IP when booting up the VM, but it doesn't last long as the reacknowledgement doesn't travel back.
So, bridging and networking is fine except for DHCP, damn.
Kai