Thanks Loic,
Yes, thats correct Kernel decides the interface to take. That is why I want to figure out if we have any way to foresee that decision ! 

I got to know a new thing: onsend_route: http://www.kamailio.org/dokuwiki/doku.php/features:new-in-3.0.x#onsend_route

I will try and make use of this route and see if it helps me select the rtp-proxy instance to use. 

Here is how it looks like:
Inline image 2
For Inbound leg all is fine, but for outbound call leg, if I know which Interface it is taking I can engage the rtpproxy instance for this.

Regards,
Sammy


On Wed, Jul 13, 2016 at 11:08 AM, Loic Chabert <chabert.loic.74@gmail.com> wrote:

Hi,

Interface selection is done by kernel when routing lookup is done, no ?
If you have the same destination and multiple interface to reach it, kernel will chose the best one (according metric values).

If you want to force trafic to go through an interface, interface must be attached to different routing table (rt_table), and with ip rule command, you can select  routing table for this packet (using packet marking).

Another recent kernel feature is VRF: https://www.kernel.org/doc/Documentation/networking/vrf.txt

Regards.

Le 12 juil. 2016 19:45, "SamyGo" <govoiper@gmail.com> a écrit :
Hi,

Question: 
Is there a function in kamailio to get the interface/listen IP kamailio would use to route a packet out for a domain / ip ?

Example: 

$avp(interface_ip) = find_interface_for_request("192.168.12.123");

And it gives me the Kamailio's Listen address that would be used for sending call out to this IP/Domain !

I've a weird situation where a multi-homed kamailio with about 7 different interfaces needs to send call out, I've so many RTProxy instances to engage but I can't decide which instance to engage since I do not know which Interface the Packet would route out from.

Regards,
Sammy



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