This question might have addressed, but not able to find correct answer in archives and I have spent enough time, so posting here. 

I want to load balance between 2-3 kamailio servers based on DNS, I don't need to worry about media just trying IM with SIP messages. 

Configured two servers with same domain alias(example.com) and able to send messages between users registered to one Node. But when i tried to send messages between users registered to two different servers, messages are not getting routed properly. When  Server A tried to reach user registered to Server:B directly, firewall is not allowing. Tried to route message to correct proxy  based on the socket details in Loctaion table, but not able to read socket details from location table, I am getting always NULL. 

I am sure,I  am doing something wrong with configuration, but not sure and also not able to find example for this on Kamailio website. I am attaching my configuration, appreciate any help.

Thanks,

VG