Hi,

We're setting up OpenSBC to sit in between asterisk and an ITSP. Phones register with asterisk directly, without going through OSBC. Asterisk registers through OSBC with the ITSP.

The purpose of the SBC is to protect the asterisk server from the ITSP. Eventually, there will be multiple asterisk servers, all talking with the ITSP through OSBC.

Outgoing calls from asterisk to the ITSP work fine. We've configured OSBC in 'B2BUpperReg Mode' and OSBC proxies the SIP messages and RTP streams as expected.

However, incoming calls from the ITSP to asterisk (through OSBC) fail. When we remove OSBC from the equation and have asterisk register to the ITSP directly, without using OSBC as an outbound proxy, all works well.

We've been searching the internet including these forums for days and played with virtually every setting in OSBC, to no avail. Hence this cry for help :)

Whatever we try, asterisk always responds with a 404 message when OSBC is relaying the SIP INVITE messages.

Asterisk debug shows this (note the null string after 'from')
[Oct 25 20:19:10] NOTICE[11186] chan_sip.c: Call from '' to extension '19000' rejected because extension not found.

OSBC routing would appear to work fine, although I'm unsure whether OSBC should be using port 5062 to talk with the ITSP.

I've compared the INVITE messages when arriving at the asterisk server, both with and without OSBC being part of the path. I'm seeing no clear differences, apart from Record-Route being present in the direct INVITE message, as well as different VIA: headers.

I'm attaching my .ini-file, as well as the INVITE messages referred to above.

Also attaching a high-level drawing of our setup.

Not sure if this is important in any way, but the IP adresses which are masked in the attachments are all public addresses, we're not using RFC1918 for any of the servers mentioned.

Many thanks in advance! It's much appreciated.

James