Probably port mapping problems

[340742]

Hello everyone,

I have the following setup

Internet -- Router -- SPA3000 & Siemens C450ip

My Spa3k listens and operates at port 5060 while my c450ip operates at port 5062.
When someone calls me at my VSP account through voxalot and I answer the phone (c450ip) I don't hear anything, but the caller still hears the phone ring while all phones in my home stop ringing (also those on the spa3k)

I have forwarded port 5060 to my spa3k and 5062 to my c450ip.

Is it just something not possible or do I need to open up more ports to my c450ip? I have setup port 5004 as RTP port in c450ip, but what looks weird to me that it's only 1 port but then again, i'm not sure if this should work or not.

Anyone knows if and how I can solve this?

BTW when I pickup the phone connected to my spa3k the conversation is okay!

Edit: When I directly put my VSP into my c450ip while using the same port settings, everything works fine, so it's only when registering to voxalot this problem exists.