Re: [libvirt-users] what interface does virbr0 forward message to?

On 11/26/2012 04:48 AM, Timon Wang wrote: That command won't show anything relevant to the question. The virbr0 bridge created by libvirt for the default network is not attached directly to any physical interfaces, so brctl will not show anything other than guest tap devices connected. All traffic from guests connected to a libvirt NATed network like the "default" network must go through the host's IP routing stack to get to the outside, and that is where the decision is made (on a per-packet basis) about which interface to use for egress. So the answer is "each packet will be sent out the appropriate interface for that packet's destination address, according to the host's IP routing table." Note that you can limit the outgoing traffic from a particular network to only be allowed on a particular interface (by adding a "dev='ethX'" attribute to the <forward> element of the network), but that will only serve to block traffic that would have been forwarded via other interfaces, it won't re-route it to the allowed interface. (BTW, please don't ask a new question as a reply to an unrelated earlier message to the list - even if you change the subject, any proper email client will bury it in the replies to the original message. Instead, create a new message.)