I am using virt-manager and created bridge at host .
My host nw interfaces is
auto br0
iface br0 inet static
address x.x.x.178
network x.x.x.0
netmask x.x.x.x
gateway x.x.x.x[gateway of eth0 earlier]
bridge_ports eth0
bridge_fd 0
bridge_hello 2
bridge_maxage 12
bridge_stp off
#dns-search google.com
dns-nameservers x.x.x.x x.x.x.x 

with this config 

1] net inside host is working
2]net inside vms created using nat is working but i have to manually ser interface file inside the NATD vm.
3] when i create virtualnetwork in routed mode using shared physical device br0 and assign vm to it 
the net inside vm not working .
4] created virtual network using only routed mode with any physical device instaead og br0 still net inside vm not working. 

I followed documentation on libvirt site .

I want vms indifferent nw should communicate with each other like net1 and vm1 can ping vm2 in net2 .