[CentOS-virt] DHCP for Xen VMs

Mon Mar 24 13:57:06 UTC 2008
Ross S. W. Walker <rwalker at medallion.com>

You might want to check iptables in the dom0.

I believe iptables gets set on eth0 before it 'pivots' to peth0 and I doubt it flushes it and retargets it to the new bridged eth0 afterwards, so the dhcp traffic may appear as unsolicited and dropped on dom0 as it enters the bridge.

If that turns out to be the case you will need to have iptables stopped right before the creation of peth0 and restarted afterwards (and maybe file a bug report too).


----- Original Message -----
From: centos-virt-bounces at centos.org <centos-virt-bounces at centos.org>
To: centos-virt at centos.org <centos-virt at centos.org>
Sent: Mon Mar 24 09:41:42 2008
Subject: Re: [CentOS-virt] DHCP for Xen VMs

Ross S. W. Walker wrote on Sun, 23 Mar 2008 19:29:47 -0400:

> Assuming you have a DHCP server on the local net, maybe ip tables in the dom0 
is blocking the dhcp traffic?
> Did you configure xend to do bridged or nat'd? Default is bridged.

Well, networking *does* work if I set an IP address manually and as I can reach 
it then from other machines it must be bridged. The problem is that I don't get 
an IP address when using dhcp :-(
I wasn't aware that iptables is on and preconfigured in a domU that got setup 
with CentOS 5.1 virt-manager. Unfortunately, shutting it off doesn't solve the 
problem. Logging shows that the server gets a request from that MAC address and 
offers an IP address, but the client doesn't receive it. There's no firewall 
between the two, but the offer doesn't get back to the client somehow.


Kai Schätzl, Berlin, Germany
Get your web at Conactive Internet Services: http://www.conactive.com

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