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Solved Remote STUN phones not ending call

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Spencer Chance

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Hi all,

Preface: I have almost no experience with remote phone setups an am a total noob.

I have a few remote employees who have Yealink phones configured to work over STUN/Direct SIP (connecting to public static IP where the PBX is). All of the phones and extensions are configured for sRTP and deliver SIP transport with TLS.

Everything generally works well, but the remote phones will not terminate calls. It takes the other end of the call to terminate the call. The same thing happens when the remote phones leave voicemails to other extensions -- they are not terminating.

Under the extensions, I have ensured that the remote phones have different local RTP audio ports, but i'm not sure if i am missing something else.

Does anyone have any experience or recommendations for me?

Additionally, should the remote phones still need to leverage 5060 even if all traffic should be over 5061 and the other RTP ports?
 
Is this an issue that just started, out of the blue, or has been there from day one?
With more than one, maybe two, STUN sets at a location, you are asking for possible problems. In many cases it can come down to the remote router, and not only port forwarding, but how well that router is able to deal with (keeping track of) multiple SIP devices that reside behind it. I would highly recommend the use of a very inexpensive Raspberry Pi SBC.

https://www.3cx.com/docs/3cx-tunnel-session-border-controller/
 
Thanks Leejor,

This has been a problem since day one. I do only have one phone at each remote location, so I don't think that is the issue.

I have looked into the SBC, but am trying to avoid it (even though it is the preferred route, heh). I need to test further with regard to TLS vs UDP
 
With one phone at each location, and multiple sites having the same issue, you have to look at the common denominator. Either a set issue (if all the same make/model sets), perhaps an option, or firmware...or, the problem is at the 3CX PBX end.

Have you run (successfully) the 3CX Firewall checker? Do you use any other model of set (3CX softphone?), at a remote location? If so, do these devices have the same issue?

Have you (factory) reset and re provisioned the sets?
 
Hello @Spencer Chance

Switch a phone back to UDP and port 5060 and see if that resolves the issue. If the issue persists then you can a wireshark capture and check the signaling between the phone and the PBX.
The strange thing here is that it seems that calls can be answered and placed so hanging up a call should not be an issue. Make sure that your phones are on the latest supported firmware from 3CX and try again.
 
Hello @Spencer Chance

Switch a phone back to UDP and port 5060 and see if that resolves the issue. If the issue persists then you can a wireshark capture and check the signaling between the phone and the PBX.
The strange thing here is that it seems that calls can be answered and placed so hanging up a call should not be an issue. Make sure that your phones are on the latest supported firmware from 3CX and try again.

I will test drive it this weekend -- I am optimistic that doing this will fix the issue, but the Wireshark capture should tell all.

I'll keep you guys updated on what i find
 
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Can confirm that bringing everything back to 5060 and UDP fixes the issue. Very odd. More info to come
 
So the first thing i'm noticing is that when the phone is set to port 5060 using UDP, the remote extension shows up under the phones list with it's public IP. When using 5061/TLS, it shows up with the local IP of the phone on the remote network.

Seems like a NAT issue, but the firewall test passes just fine.
 
When using 5061/TLS, it shows up with the local IP of the phone on the remote network.

Which means that 3CX cannot contact the phone, it requires the Public IP. May be a STUN setting/configuration/option, on the set.
 
The Solution!

Just to clarify, the phone would kill a call before i answered, but once the call is actually hot, then the remote extension will not terminate the call. I am using a Yealink T41S phone on firmware 66.83.0.55, as well.

After digging through Wireshark, I was not seeing anything that really stood out, except I was noticing that the phone was not sending a BYE.

I had also tested the remote phone using just regular TCP instead of TLS to port 5060 (and created the firewall rule for it) but no dice.

Anyways, I googled about Yealink not sending a BYE and found http://forum.yealink.com/forum/archive/index.php?thread-3885.html, which said that you had to make sure to fill out the Outbound Proxy Server on the phone. After doing this, everything is working perfectly.

Still feeling foolish for not catching this earlier, but i didn't think i needed it (shrugs)

upload_2018-12-14_15-24-31.png

Thanks for your help, everyone!
 

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Glad to see the issue has been resolved and thank you for updating the thread with your solution.
 
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