running two bird daemons which listen on loopback IP

Hi, For testing purposes I want to run two bird instances which listen on two different IPs. Those IP addresses are assigned to loopback interface(Linux box). I have configured BGP but each daemon is waiting the other to become neighbor. I run tcpdump on loopback interface and I don't see any network traffic, and I am wondering if using loopback inteface isn't supported. Cheers, Pavlos