[SR-Users] rport parameter in VIA header in uac remote registration

Alex Balashov abalashov at evaristesys.com
Wed Nov 11 08:48:31 CET 2020

Try add force_rport() to the portion of your configuration which 
processes the incoming requests in question.

On 11/11/20 2:38 AM, Jetse Verschuren wrote:
> Hi,
> I'm currently trying to connect Kamailio, running in docker, to my 
> FritzBox. The FritzBox is the modem provided by my ISP, with a builtin 
> voip server which I can use to dial out (basically a PSTN gateway). In 
> my setup I have a custom router/firewall/NAT between the FritzBox and 
> the server.
> When I connect LinPhone to the FritzBox, from behind the NAT, it works 
> fine. But when I use the Kamailio uac remote registration,  I don't get 
> a response. After some investigation with wireshark, I found that the 
> the SIP response from the FritzBox comes on the wrong port, and gets 
> rejected by the NAT. The request comes from port 1025, but the response 
> is sent to port 5060. I compared the requests from LinPhone and 
> Kamailio, and combined with some research, found it probably was the 
> rport option in the VIA header. From what I read, it basically signals 
> the uas to use the source port to reply to, instead of the port 
> indicated in the request, which would be necessary to effectively go 
> through a NAT.
> After reading a lot of documentation (and even parts of the source), I 
> wasn't able to find an option to enable this option. Is there some 
> option I completely missed, or is it not possible? Or am I completely 
> wrong in my "diagnosis"?
> Thanks in advance,
> Jetse
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Alex Balashov | Principal | Evariste Systems LLC

Tel: +1-706-510-6800 / +1-800-250-5920 (toll-free)
Web: http://www.evaristesys.com/, http://www.csrpswitch.com/

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