[Serusers] round robin routing

I need a solution that can implement round robin routing.... ive used the gflags module to do this, and it routes my snom phoens two different servers (im using SER as a load balancer) currently just doign a simple redirect server. Here are my problems...phones routed to the same server cannot call each other..... also...when reciveing an incoming call on DID from PSTN.... if the phone registers to one server.... and there are three...how can i have it route to the proper server of where the phone is registered? Finally how would I make calls between servers (they all have the same config) with out going to the PSTN termiantion point and going back in??