[Serusers] nathelper & rtpproxy

Guillaume du Manoir gdumanoir at cvf.fr
Fri Sep 3 12:43:46 CEST 2004


Hello,

I have a question concerning the nathelper module and rtpproxy.
Here is the network layout :

Sipphone1 <----> Firewall with NAT <------> SER with nathelper <---> Sipphone2
(public IP)      public IP/private IP       + rtpproxy               private IP
                                            (private IP)

I understand that the regular way of using nathelper/rtpproxy is to
put them on a dual interface computer (one internal interface and one
external one). In my case it is not possible, the SER box is inside
and has only one internal interface.

I am puzzled at how I should configure SER and rtpproxy to allow
sip calls from outside to inside.

Currently the sip trafic is fine, ie I call from outside to inside,
and my internal phone is ringing. The problem is with the rtp trafic.
I can't find the way to make nathelper/rtpproxy change the rtp IP to be
used for the call.

I am using CVS version of ser/nathelper/rtpproxy. Whatever the config
I try (examples, and mails from this list) the IP in the sip packet
stays the one from Sipphone2 (where it should me the external
interface ip from the firewall).

Another way to formulate my problem is : how could I tell nathelper
which IP it has to use to replace Sipphone1's ip for rtp trafic ?

Thanks !
Guillaume





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