Kai Schaetzl wrote:
Ross S. W. Walker wrote on Tue, 1 Apr 2008 10:16:38 -0400:
dnsmasq is going to filter out the incoming dhcp requests as it acts as a dhcp server itself. Try disabling dnsmasq, or move your VMs off of virbr0 onto xenbr0.
I wrote dnsmasq is killed then ;-) I started service libvirtd and then killed dnsmasq and made sure it wasn't running. Then I tried. And the virbr0 is not used anyway. However, something that libvirtd does seems to switch on some extra forwarding that helps the broadcast packet to travel from peth0 to eth0 which otherwise it would only do if it had an IP address target. I have now stopped libvirtd as well and it still works, even for a VM that I start after that (which means I can rule arp table out as its MAC address was unknown). And iptables does not show any forwarding rules once I stop libvirtd. The NAT stays active stopping libvirtd, but I killed it with iptables. Still it works. So, there must be something that switches this on. I'm sure if I reboot the host the problem is back.
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.
-Ross
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