2012/5/20 Salman Malik <[email protected]> > Thanks Reid, please find the inline comments. > > > ------------------------------ > From: [email protected] > Date: Sun, 20 May 2012 01:56:05 -0700 > > Subject: Re: [ovs-discuss] why vm can't ping host eth1 > To: [email protected] > CC: [email protected]; [email protected] > > On Sat, May 19, 2012 at 3:42 PM, Salman Malik <[email protected]> wrote: > > Thanks a lot Reid. That was one awesome explanation. Few more questions: > > 1) In the first figure VMs can not communicate with the outside world > (except using NAT) ? > > > Yup. I'm not sure what NAT would mean in this context, all tap1/2 traffic > will be going directly into br0, and br0 (as shown) has no way to get to > the outside world. > > I was thinking if traffic from any VM could go through bridge interface > and then traverse through the IP stack to go out to any ethX? >
I think what Salman wants, is having VM packets go out this physical box through eth0/eth1, without adding eth0/eth1 to ovs bridge. That should be achieved through NAT with the help of iptables. I think the default network "virbr0" of libvirt is a good example. For virbr0, there's no pNic(eth0/eth1) connected to the bridge. But VMs you created by virt-install do have network access out of this physical box. Libvirt achieves that by adding NAT on iptables, providing DHCP service automatically to VMs(192.168.122.0/24 by default, make virbr0 work as a gateway), and it has dnsmasq configured for DNS service. I didn't go through libvirt network and virbr0 deeply, may the above info be helpful to you, Salman. And feel free to correct me if I got something wrong. Thanks very much. Best, Robin
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