Just to add here, double rr with putting the interface details in them using the record_route_preset (https://www.kamailio.org/docs/modules/devel/modules/rr.html#rr.f.record_route_preset) might be the way to go here. 

This will allow the BYE to have the correct routes to get back out hopefully. 

So on initial invite from private: in rr header 1st rr is from public, 2nd rr is private

and on initial invite from public: in rr header 1st rr is from private, 2nd rr is public

This orders the rr headers so on the way back they come in correctly if that makes sense.

I do this at the initial Invite and it works fine for me, but your mileage may vary. 

Hope this helps,

John. 

On Tue, 24 Jun 2025 at 10:25, Sergei Safarov via sr-users <sr-users@lists.kamailio.org> wrote:

Will be fine to check SIP messages.

Here is important Route, Record-Route and contact header values.

Sergey.

On Mon, 2025-06-23 at 20:24 -0500, Dustin Marquess via sr-users wrote:

All,

I've tried searching and have found similar posts before, but I have yet to find a real 'solution'.

I'm running Kamailio 6.0.1 & RTPEngine 13.3.1.7 (on a Linux VM)  as a "SBC" (at home) using the config from: 
https://github.com/voiceboys/sbcOS/blob/version_2.0/var/www/html/alpine/config/a0%3A36%3A9f%3Ae7%3A6a%3Ae2/etc/kamailio/kamailio.cfg

Except that I've added the following:

mhomed=1
modparam("rr", "force_send_socket", 1)

The SBC is dual-homed: one interface on the local LAN and another interface directly on the Internet/WAN (real public IP).

Everything works fine, EXCEPT if the remote end (the side on the WAN/Internet) hangs up first. If they do, the BYE never makes it past Kamailio to the local PBX and/or phone.

https://users.openser.narkive.com/1aK7n8Il/sr-multihomed-kamailio-and-enable-double-rr#post8 suggests to use $sht to save the information needed, but I have no clue where in the config to put that.

Any help would be greatly appreciated.

Thanks!

-Dustin