[SR-Users] Kamailio behind NAT - best practice

[Klaus Darilion]

Hi!

Up to now I could avoid Kamailio setups with Kamailio behind NAt. But 
this time I have to deal with it. That's why I want to ask what others 
did as best practice.

The scenario is:


Asterisk 1----\       Kamailio+RTPPROXY
                \         |10.10.0.2
Asterisk n------\        |
                  --------|------------- FW --SIP-trunk--- ITSP
Freeswitch 1----/              10.10.0.1   public-IP
                /
Freeswitch n--/
            10.10.0.x

Kamailio and rtpproxy have a private IP. Internal communication uses 
private IPs, external communication uses a public IP which is NATed 1:1 
to Kamailio's IP address. No registrations, just forwarding of messages.

Using the global "advertised_address" setting with the public IP does 
not work, as there is also internal communication. Using 
set_advertised_address() is also cumbersome.

So it seems, the easiest solution would be to use 2 sockets on Kamailio, 
e.g. port 5050 and port 5060. Then I could use the listen with dedicated 
advertised addresses:
listen=udp:10.10.0.2:5050
listen=udp:10.10.0.2:5060 advertise pu.bl.ic.ip:5060

If I understand it correctly, this should solve all issues with 
Record-Routing and Via-headers.

For RTP-Proxy it seems necessary to detect the direction of each message 
and set the IP address in rtpproxy_manage("","ip.add.re.ss") manually.

Thus, it seems straight forward - or do I miss something? Any comments 
and practical experience?

Thanks
Klaus