[OpenSIPS-Users] Two OpenSIPS proxies issue

Duane Larson duane.larson at gmail.com
Wed Jul 4 21:49:35 CEST 2012

I have the following scenario

LAN <-> OpenSIPS/SBC <-> INTERNET <-> OpenSIPS/Proxy

I have the OpenSIPS/SBC device because the firewall that is protecting the
LAN doesn't play well with SIP.  It has the following IPs (LAN =, WAN (99.xx.xx.161).

The OpenSIPS/Proxy device sits on the internet and has the following IP

All of the devices on the LAN point to the OpenSIPS/SBC as their proxy and
then the OpenSIPS/SBC relays all requests to the OpenSIPS/Proxy.

The issue I am seeing is that when a call is set up after the Callee sends
the 200 OK the Caller sends the ACK but the ACK is never getting to the
Callee.  So the Callee keeps sending 200 OKs and eventually when someone
hangs up the other person doesn't know.

I see that when the Caller sends the ACK it is sent to the OpenSIPS/SBC LAN
address, then the OpenSIPS/SBC sends the ACK to the OpenSIPS/Proxy, then
the OpenSIPS/Proxy sends it back to the OpenSIPS/SBC WAN address.  All of
that is good but the next thing that happens is that the OpenSIPS/SBC sends
the ACK not to the Callee but to its WAN interface.  I know this has
something to do with my VIA headers but I am not sure how my config is
messed up.

Here is the siptrace of the call


Here is the current config on the OpenSIPS/SBC box


Any ideas where I've messed up?
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