I have two branch routers connected to central site over frame relay network.
Now i've put fxs cards in all three routers and want voice connectivity among all three routers.
Basically its like hub and spoke.. one central site connecting on sub-interface to two other sites on frame network.
What is the best way to configure these three routers ???
Your requirements seem vey simple so my suggestion is to keep the configuration very simple as well. You need a dialplan which allows each site to call the other two sites.
I would suggest you use voice over ip OVER frame, rather than just voice over frame. There is a little bit more overhead, but ease of troubleshooting and configuration makes it worth it.
You need two voip dial peers at most to differntiate what destination patterns go to which site and one pots dial peer for each FXS port that you have a phone attached to.
For QOS, i suggest using frame relay traffic shaping and if necessary LLQ.
Hope this answers your question.