[root@localhost ~]# cat qemubridge.sh 
sh /root/kvm.load.sh
ifconfig $1 0.0.0.0
brctl addbr br0
#ifconfig br0 192.168.2.197 netmask 255.255.255.0 up
#route add default gw router
brctl setfd br0 1
brctl sethello br0 1
brctl addif br0 $1
sleep 1
ifconfig br0 up
killall dhclient
sleep 1
dhclient br0
qemu-system-x86_64 -hda /media/windows/windows.img -m 384 -net nic,vlan=0 -net tap,vlan=0,ifname=tap0,script=/etc/qemu-ifup
ifconfig br0 down
brctl delbr br0
killall dhclient
sleep 3
ifconfig $1 up
dhclient $1
sh /root/kvm.unload.sh
[root@localhost ~]# cat /etc/qemu-ifup 
#!/bin/sh

echo "Bringing up $1 for bridged mode..."
switch=$(ip route list | awk '/^default / { print $NF }')
ifconfig $1 0.0.0.0 promisc up
brctl addif ${switch} $1
sleep 2
[root@localhost ~]#