Rejection from a server?

hy all
i have configured both of the asterisk servers. manipulated iax and extensions. now both the servers has registered them selves but when i dial extension of the other server i.e server 2 it is rejected by it. server 1 send request bu it is rejected by server 2. what do u think the problem will be. either
plzz help me out. i shall be thankfull to u

Can you give some of the output from the console or the log file? Is it possible that the call you are passing from SERVER_A to SERVER_B does not have a valid extension in the SERVER_B context? You have to have the dial plan built out on the far end to handle the call.