use the bridge-utils tool to setup bridge network for KVM.

use the bridge-utils tool to setup bridge network for KVM.

1.install the bridge-utils tool.
# yum install bridge-utils

2.check the brctl man help.
# brctl --help
Usage: brctl [commands]
commands:
	addbr     	<bridge>		add bridge
	delbr     	<bridge>		delete bridge
	addif     	<bridge> <device>	add interface to bridge
	delif     	<bridge> <device>	delete interface from bridge
	show      	[ <bridge> ]		show a list of bridges
	showmacs  	<bridge>		show a list of mac addrs
	showstp   	<bridge>		show bridge stp info
	stp       	<bridge> {on|off}	turn stp on/off

3.create a bridge and add the eth0 interface to the bridge.
# brctl addbr switch
# brctl addif switch eth0

4.clear the eth0 ip addr and specify the ip addr for bridge.
# ifconfig eth0 0.0.0.0
# ifconfig switch 10.66.106.12 netmask 255.255.255.0

5.setup guest network up/down script.
# cat /etc/qemu-ifup
#!/bin/sh
switch=switch
/sbin/ifconfig $1 0.0.0.0 up
/usr/sbin/brctl addif ${switch} $1 

6.show a list of bridges and the tap0 is the bridge port which is connected by the VM.
# brctl show switch
bridge name	bridge id		STP enabled	interfaces
switch		8000.a0d3c1fbb474	no		eth0
							tap0