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KVM Routing Bridge




Posted by SPaReK, 02-19-2015, 02:17 AM
I've got a CentOS system that I am trying to create a network bridge for KVM guests. I have one Ethernet interface: IPADDR: 101.X.X.20 GATEWAY: 101.X.X.1 I have secondary IPs: 72.X.X.31 72.X.X.32 72.X.X.33 72.X.X.34 I'm wanting to assign the KVM guest the 72.X.X.31 IP address. But I cannot get that to route. I need to set the Host to recognize the 72.X.X.31 IP and forward that on to the KVM guest. I then need the guest to be able to access the Internet through the 101.X.X.1 gateway. How do I set up the bridge to accomplish this?

Posted by devops036, 02-19-2015, 08:23 PM
What you try to achieve is possible: I did it What you need: - the MAC address associated with each of your VM IP addresses (72.X.X.31, ...) (otherwise nothing will work, the host couldn't make the association), - a configured bridge called br0 (change the name accordingly). Follow these steps: - stop your VM - edit your VM configuration file (normally in the /etc/libvirt/qemu directory) - search for - replace with - restart the libvirt daemon service libvirtd restart - start your VM - connect to your VM through the console (virsh console vm) - edit the /etc/sysconfig/network-scripts/ifcfg-eth0 file - assign the new MAC address to the HWADDR variable, the desired IP address to the IPADDR variable, the desired gateway to the GATEWAY variable and the NETMASK 255.255.255.255 (or PREFIX=32) IMPORTANT! If your VM is in CentOS 7, it should work straight. If your VM is in CentOS 6, you've got an additional tricky step (don't ask me for CentOS 1 to 5, I didn't try and don't want to!). You have to create a file called /etc/sysconfig/network-scripts/route-eth0 and paste the following lines with your default gateway: 101.X.X.1 dev eth0 default via 101.X.X.1 dev eth0 It worked for me, it should work for you: I've got no superpower! Good luck!

Posted by SPaReK, 02-21-2015, 07:09 PM
I was able to get this figured out. My solution is below. The key part I seemed to be missing was the parts in the /etc/sysconfig/network-scripts/route files. On the HOST: /etc/sysconfig/network-scripts/ifcfg-eth0 /etc/sysconfig/network-scripts/ifcfg-br0 /etc/sysconfig/network-scripts/route-br0 On the GUEST: /etc/sysconfig/network-scripts/ifcfg-eth0 /etc/sysconfig/network-scripts/route-eth0



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