Hi,
I have a SER + Mediaproxy. I have not any problem the call between SIP clients (behind or not the NATs)
but when I try to call to PSTN (via cisco) I only have RTP traffic from SIP client to PSTN.
 
Summarizing, the path of rtp traffic would have to be from:

        up:    SIP Client ----> SER ---> GW-PSTN
        down:  SIP Client <---- SER <--- GW-PSTN
 
but, really is:
 
        up:    SIP Client ----> SER ---> GW-PSTN
        down:  SIP Client <------------- GW-PSTN
 
I use the command:
 
     rewritehostport("212.xxx.xxx.xxx:5060");
 
when I match a geographic number.
 
The complete scheme is:
 
    SIP Client ---- NAT --------- SER+Mediaproxy -------- SIP Server --- GWPSTN
 
 
 
Some idea?
Thanks,
 
--
Alberto