[CentOS-virt] xenbr0 isn't created anymore

[Kai Schaetzl]

<E2BB8074E <E2BB8074E5500C42984D980D4BD78EF9022A706F at MFG-NYC-EXCH2.mfg.prv>
Reply-To: centos-virt at centos.org
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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.

Kai

-- 
Kai Schätzl, Berlin, Germany
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