1 Replies Last post: Jul 24, 2007 5:31 AM by Guest  
Guest

Jul 24, 2007 4:39 AM

[OpenSIPStack] OpenSBC behind NAT/router

Hi all,

I have a bit of a tricky problem and am not sure if OpenSBC can handle this setup. The network config is as follows

Office: Office Home
SBC (10.17.20.4) Router/NAT Router/NAT SIPPhone

Now the office NAT has port forwarding rules to send the SIP traffic to the SBC. The SIPPhone can send the invite to the SBC which internally forwards it to a voice service. The SBC sends back the 200 OK and ACK follows. So the SIP sginalling works, but the SDP offer/answer is not quite right.

Obvioulsy the SDP in the invite has the wrong (sipphone-local) ip address. The SBc should be able to correct that. But the SDP answer from the SBC also shows it's internal IP address(10.17.20.4).

Now the question i have is if it is possible to configure the SBC to use the public ip address in the SDP. Furthermore, i'd like to know if it is possible to configure a port-range for the RTP traffic so that i can put some forwarding onto the NAT/router.

A last question would be, whether i'm able to get this setup to work?

does somebody have some experience or give some advice?

cheers

roland


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Guest
1. Jul 24, 2007 5:31 AM in response to: Guest
Re: [OpenSIPStack] OpenSBC behind NAT/router
openSBc isn't really made for this setup. OpenSBC is intended to be
used either as a bridge between multi-homed networks or as a far end NAT
traversal server. These two setup requires that OpenSBC itself is not
the subject of NAT.

You may try "Static RTP Media Address" in the general parameters
config. Set the value to the public address of your NAT router. As
for the port number, OpenSBC starts at 30000 onwards for RTP and no,
there isn't any provision to set the port range. This however can
easily be achieved with some code modification. Let me know if you want
to stretch it a bit further.

Roland Auckenthaler wrote:

Hi all,

I have a bit of a tricky problem and am not sure if OpenSBC can handle this setup. The network config is as follows

Office: Office Home
SBC (10.17.20.4) Router/NAT Router/NAT SIPPhone

Now the office NAT has port forwarding rules to send the SIP traffic to the SBC. The SIPPhone can send the invite to the SBC which internally forwards it to a voice service. The SBC sends back the 200 OK and ACK follows. So the SIP sginalling works, but the SDP offer/answer is not quite right.

Obvioulsy the SDP in the invite has the wrong (sipphone-local) ip address. The SBc should be able to correct that. But the SDP answer from the SBC also shows it's internal IP address(10.17.20.4).

Now the question i have is if it is possible to configure the SBC to use the public ip address in the SDP. Furthermore, i'd like to know if it is possible to configure a port-range for the RTP traffic so that i can put some forwarding onto the NAT/router.

A last question would be, whether i'm able to get this setup to work?

does somebody have some experience or give some advice?

cheers

roland

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Still grepping through log files to find problems? Stop.
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