SIP: PAP2T doesn't support dynamic IP?

Question

I have the Linksys PAP2T with firmware v5.1.6(LS).

I want to make it connect to a SIP gateway (LANCOM 1823 VoIP) through internet (both sides use an ADSL connection). The problem is that the connection where the LANCOM is, uses dynamic IP.

If I enter the current IP of the LANCOM, the PAP2T connects to it and works flawlessly (until IP resets by the ISP). I've tried a DynDNS address to always have the current LANCOM's IP available, but the problem is that if I put that as proxy (instead of the IP) to the PAP2T, it returns error that it can't even find the LANCOM.

Any suggestions to make the PAP2T connect to the LANCOM without resolving to switch into a static IP?

Answer 1

It seems that it was needing an external STUN server (I've used the free stun.voipvoip.com) and enabling only the "Substitute VIA Addr" option (everything else must be set to "no").

Now everything works alright with both DynDNS and no-ip!