Port forward problem behind two routers ATA

Qnewbie

My case is port forwarding problem of an ATA (SPA1001) with 6+1+2 scheme. The ATA is behind two routers.

The first router is combo of modem and router(Zyxel), the second one is Dlink N router. I put the SPA1001 at the DMZ for Dlink. I don't have the access to the first router.

I got it work once. Currently I can access the admin web of SAP1001 from outside and the sip signal goes thru both routers and I get ring tone at the other end. However, the RTP stream is blocked. Audio problem again.

Qnewbie

Provisional solution is:
1. First modem-router combo acts as modem bridge. It provides the room for the second router as "first" router.
2. The second router turns SIP application-level-gateway(which makes thing worse than help!) off and puts the SPA1001(static ip within LAN) in the DMZ.

It is under test. The result sounds promising.

角色

In order to isolate the problem, how about the result with the Zyxel router + SPA1001? Does it work?

Qnewbie

Do.

The 6+1+2 scheme includes the stun server. Stun server is enabled.

角色

Have you tried any STUN server?

YH