I had to rename my bridge connection name one day, which was used by a vm. Later i realised that because of missing bridge connection "br0" my vm fails to restart. I tried changing interface name via virt-manager gui but no use.

tried virsh command line as well, but no use.

$ sudo virsh start VM1
setlocale: No such file or directory
error: Failed to start domain VM1
error: Cannot get interface MTU on 'br0': No such device

After spending some time on redhat webiste, i learnt that bridge connection name "br0" has to be replaced with new one by editing the vm config file. So here is what i did. 

$ virsh edit VM1

File looks like this.
$
Change it to 
$
Then try starting vm and it should work if you didn't messup config file. gil ... s