[CentOS] Connecting ethX devices directly to a KVM/QEMU guest OS (no bridging)

Tait Clarridge tait at taiter.com
Thu Jan 19 18:44:53 UTC 2012

> But a new problem arises ... one of the m0n0wall instances needs to use 
> DHCP to get a dynamic IP from my ISP (the others are static, so they're 
> ok).  How do I get the bridge to proxy the DHCP request and forward the 
> response to the VM guest?  I brought up a test instance of m0n0wall but 
> when it asks for an IP on its WAN side, the result is  so it 
> would appear the request never makes it to the ISP.
> As a sanity check, I configured the WAN-side bridge to use DHCP and that 
> worked, but it's the m0n0wall VM guest that needs to make the request, 
> not the CentOS host.
> Suggestions anyone?  In the mean time, I'll keep looking for a solution.
> Thanks,
> Chuck

Hmmm. Is the bridge up and you can see the interface attached to it from
running "brctl show" and "ifconfig"? Could you attach that output?

If yes, then I would do a packet capture on the CentOS host on the eth
interface attached to the bridge to see if the request makes it out.

I'm running XEN at home and I have a very similar setup where I pass a
VLAN from my switch that a provider modem is connected to into a bridge
and it gets DHCP no problem (as long as the bridge and dot1q
subinterfaces show up in ifconfig).

The bridge should automatically send all the traffic out regardless of
protocol, I doubt ebtables would be actively blocking anything as well
and same goes for the ISP locking down with MAC addresses.

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