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.

角色

Have you tried any STUN server?

YH

Qnewbie

Do.

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

角色

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

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.