Registering Remote Users through SBC

I’ve been wrestling with a problem and I can’t seem to pinpoint the issue. My setup:

AudioCodes VE SBC - 7.20A.204.222 - fqdn = audiocodes. mydomian .com (resolves internally and externally)

FreePBX - - fqdn = pbx. mydomain. com (resolves internally)

Asterisk - 15.5.0

Using pjsip for UDP, TCP and TLS

I have a pjsip trunk setup between my PBX and the SBC. Trunk name is ‘AudioCodes’, context is set to from-ptsn, and I’m using the FQDN of my SBC in the trunk configuration. Local users register directly to the PBX. I’m trying to allow remote users to register to the PBX through the SBC. I point remote users to the external FQDN of the SBC. When a register packet comes in, the SBC will change the host portion of the SIP URI in the To and From headers from the FQDN of the SBC to the FQDN of the PBX and then send it off. When the PBX receives the register request it replies with a ‘404 Not Found’. Checking the logs on the PBX I get the error 'AOR not found for endpoint ‘AudioCodes’ ’

Looking at pcaps from a local register and one coming from the SBC, everything looks the same, except the Request-URI for an SBC registration will still contain the FQDN of the SBC while a local registration will have the FQDN of the PBX. I feel like there’s something simple that I’m missing but can’t seem to put my finger on it.

Probably a misconfiguration on SIP domain upstream authentication.

Thanks for the reply arielgrin. Any idea where I should start looking? It seems like the traffic is flowing as I would expect. I can see the register come in to the SBC and it gets forwarded to the PBX. The PBX seems to be looking for an AOR for the trunk rather than the extension. I would assume that the PBX would just add the SBC address as a contact for the extension. It seems like it’s matching the IP address the request comes in on to the trunk endpoint and then looking for an AOR.

I’m not familiar with Audiocodes SBC but maybe this example is useful, take a look at the first example, specifically the part for nomadic wan users, pay special atention to domain setting

Also, I guess you are using PJSIP. Have you tried using CHAN_SIP?

Thanks for the help. I figured it out. In my situation I have the PBX sending calls to the SBC. My SBC handles call routing between my Skype for Business Server, PBX and SIP provider. Since my PBX was already aware of the IP of the SBC, anything coming from that IP was considered call traffic.

In all the examples I researched, none of them showed the PBX having an existing trunk to the SBC. What I needed to do was add a network interface to by SBC and send my registration traffic through that to the PBX. The PBX then considered that new IP address of the new interface as simply just a new contact object for the extension. Then I created a new routing rule to send calls destined for the extensions from the PBX to that IP Group of the remote users.

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