Cisco 7940 x FreePBX

I recently revived an old Cisco phone model CP-7940 and encountered difficulties when attempting to connect it to our FreePBX server. Unlike our other phones, such as the GrandStream models, the CP-7940 is failing to register with FreePBX. Despite verifying the correctness of the configuration, I haven’t observed any registration attempts from the device in the server logs.

I would greatly appreciate assistance in resolving this issue. If anyone has insights or suggestions on how to troubleshoot and rectify this registration problem with the Cisco CP-7940, your expertise would be invaluable.

Thank you for your attention and support.

Did you create a pjsip or a chan_sip extension? In either case, note that the 7940 uses TCP transport. Did you enable that and set the TCP listen/bind port to match what the phone is using?

If the above is correct and nothing appears in the Asterisk log, use tcpdump to check for connection attempts from the phone. If nothing there, either, capture traffic at the phone and check for outbound TCP connection attempt to the correct IP address and port.

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Thank you for your response. Enabling TCP in the PJSIP settings has resolved the issue for one phone, but unfortunately not for the second one.

Could you please review this brief log and advise on its implications? I’ve been troubleshooting diligently but haven’t yet identified a solution for this persistent problem.

[2024-01-31 12:00:34] ERROR[2368] pjproject: sip_transport.c Error processing 572 bytes packet from UDP : PJSIP syntax error exception when parsing 'Request Line' header on line 1 col 14:
465978Via: SIP/2.0/UDP;branch=z9hG4bK2acc1eb0
465981Call-ID: [email protected]
465982Max-Forwards: 70
465983Date: Wed, 31 Jan 2024 10:00:31 GMT
465984CSeq: 102 REGISTER
465985User-Agent: Cisco-CP7940G/8.0
465986Contact: <sip:[email protected]:5060;user=phone;transport=udp>;+sip.instance="<urn:uuid:00000000-0000-0000-0000-0014f2ca6306>";+u.sip!"8"
465987Content-Length: 0
465988Expires: 120
465991-- end of packet.

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