[asterisk-users] [RTP] PSTN -> Gateway -> Phone

[Vincent Delporte]

Hello

I'm using a Linksys 3102 as VoIP gateway to connect a POTS line to a PBX. I 
also have an IP phone in a remote network across the Net. The PBX + 
gateway, and the phone are both behind a NAT router.

I was wondering:

1. When a customer calls us through the POTS line and I pick up the call 
with the remote IP phone, do RTP packets go directly from the VoIP gateway 
to the IP phone, or do they go through the PBX, ie. is it...

POST <-> VoIP gateway <-> NAT <-> Net <-> NAT <-> IP phone

or

POST <-> VoIP gateway <-> PBX <-> NAT <-> Net <-> NAT <-> IP phone

?

2. Regardless of the route RTP packets take, do I have to map ports on both 
NAT routers for RTP packets to be let inside the LAN, or is STUN able to 
handle this itself? How do I know if the routers are STUN-friendly, or I 
have to map ports?

Thank you.