In this howto we will setup bridged networking to dedicate physical network device to KVM virtual machines/servers. Its best way to have local network between virtual machines and provide better performance.
1. Create a Bridge
Before it was all manual to create bridge device but now KVM provide single command to do all. To create a bridge (br0) using eth0, you need to execute following command
virsh iface-bridge eth0 br0
This will create bridge (br0) device file in /etc/sysconfig/network-scripts/ and take all settings from eth0 to configure itself with configure eth0 to use br0.
2. Stop NetworkManager
You will also need to do following in all ifcfg-* file in /etc/sysconfig/network-scripts/ to disable NetworkManager. Edit all files and make sure to have following value
NM_CONTROLLED=no
After this stop NetworkManager and start network service to start bridge at startup.
chkconfig NetworkManager off chkconfig network on service NetworkManager stop service network start
You can now create or edit your virtual machine to use bridge network device (br0).