I'm fairly new to the VoIP area but feel like I have a good understanding of the system.
I have a Polycom Soundpoint IP 600 SIP on my desk, my business partner lives 45 minutes away and has a Grandstream GXP2000 on his desk, the asterisk (1.4) server is between the two of us (outside both of our LANs) running iptables. We've opened up what we believe to be all the right ports (TCP/UDP SIP, TCP/UDP 10000-20000, and we believe they're all right because the grandstreams work)
His Grandstreams register just fine. My phones will NOT register, however. Neither the Polycom nor the XLite softphone. The only time they register is after I restart the iptables service in Linux and then after 20 minutes they de-register themselves and won't re-register.
I've been pulling my hair out trying to solve the problem, if anyone knows, please HELP!