[OpenSIPS-Users] Fix source IP in a 2-NICs router with openSIPS

[Bogdan-Andrei Iancu]

Hi Víctor,

You have to take care of 2 things:

1) signaling - for this you opensips should only do double RR to record 
the change of interface (in on priv IP and out on pub IP) - to have 
this, before pushing out the call to asterisk, do 
force_send_socket(pub_IP), so that a different interface will be 
selected as outbound.
For contact you do not have to do nothing.

2) media - insert RTPproxy which must be configured in bridging mode (to 
use 2 interfaces). And according to SIP traffic, you need to use the "e" 
or "i" flags (when invoking RTPproxy from script) in order to choose the 
proper IP for media. Like for INVITE (going from priv to pub) instruct 
RTPP to use the pub interface, for the 200 ok reply, need to use the 
priv interface.

Regards,
Bogdan

On 04/03/2012 04:31 PM, Víctor Fernández Martínez wrote:
> Hi! I'm trying to set up OpenSIPS in a router with 2 NICs that performs a
> dynamic NAT. It will receive requests from the UACs on eth0 (NIC behind NAT)
> and should forward them through eth1 (public NIC) to an Asterisk outside of
> the NAT. I'm not allowed to configure the Asterisk. I have also configured
> rtpproxy and would like to use it in order to traverse the NAT. I have
> openSIPS listening on both NICs, so the UACs inside of the NAT connect
> directly to the socket of openSIPS in eth0.
>
> The question is: I have tried to use fix_nated_contact() and fix_nated_sdp() but
> they don't actually change the source IP, so I get no RTP traffic. Seems like
> openSIPS doesn't realise there is a NAT, since it receives the requests
> directly through its socket in the LAN. So when I use
> rewritehostport("IP_OF_ASTERISK"), Asterisk is getting the LAN IPs instead of
> the IP of eth1, which is the public IP. I'm using force_send_socket() to force
> openSIPS to send the SIP messages to Asterisk through eth1. Is there some way
> to fix the IPs so Asterisk gets the public IP (eth1)?
>
> Thank you very much in advance.
>
>
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-- 
Bogdan-Andrei Iancu
OpenSIPS Founder and Developer
http://www.opensips-solutions.com