Issue with T46S and 3CX Mobile Client

[pitrickzul]

Hey Guys,

Having a weird issue with extensions using the T46S (latest firmware supported by 3CX) and the 3CX Mobile Client.

3 out of 5 calls don't ring on the phone but they ring on the mobile client only. If you logout of the mobile client, the phone doesn't even ring at al. All extensions are set to available. We have 3 T46S in the office and they are all having the same issue, everyone else uses T41S or T40G and i have a T48S and i do not have this issue, only seems to affect T46S.

Do you guys have any ideas?

 

[Christopher Reagoso]

Cloud hosted 3cx, or on-premise 3CX?

If cloud-hosted, are you using the 3CX SBC?

 

[pitrickzul]

cloud, STUN only.

All phones are static IP with different SIP and RTP ports

 

[Christopher Reagoso]

On your router at your office:

1. Disable SIP ALG
2. Ensure you're using consistent NAT
3. Make sure UDP timeout is set to 300 seconds or higher (could probably go lower, but that's safe)

If that doesn't work or you can't get to those settings..., set up the 3CX SBC and you'll be in good shape probably.

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

Happy hunting.

 

[pitrickzul]

What do you mean by Consistant NAT?

 

[pitrickzul]

Ok finally getting more info..

This is not only affecting my T46S phones.

Im getting people with other models experiencing the same issue. This is on external calls only.

We use 2 different supported SIP providers. Thinktel and VoicemeUP. However, most of my incoming calls are on Thinktel and most of my outgoing calls are on VoicemeUP.

Call comes in, person's mobile client rings.. wait 15 secs and eventually, the phone rings (both devices on the same network)

Also, sometimes there's a 10 to 15 secs delay in dialing external calls.


All internal calls are working correctly. We have 19 offices and 3CX is hosted. all internal is good only issue with external.

SIP ALG is obviously disabled.

We didn't have this issue earlier this week, this started 2-3 days ago, nothing was modified on the network.

 

[Marari]

I can't speak to Thinktel's support, but VMU has a great support team. I've engaged them several times in the past to help troubleshoot a few random issues. You may want to have a chat with them on the delay for outbound calls.

If possible, introduce an SBC (an old PC running debian linux and the instructions from 3CX for setup will do). If you're not a linux guy, then a windows PC will do as well - there is a windows SBC from 3CX as well.

If your problem goes away, you know the issue is the STUN provisioning. If the problem still exists, wireshark may be your friend.

 

[pitrickzul]

i've deployed a debian9 SBC and put a couple of phones on it. Will report back.

 

[pitrickzul]

So far so good, all delay is gone..

We've been running for 1 month with STUN only, never noticed any issues.. Why all of a sudden, we don't know...

Is it safe to remove the PBX Delivers Audio option when phones are connected by SBC?

 

[Marari]

So far so good, all delay is gone..

We've been running for 1 month with STUN only, never noticed any issues.. Why all of a sudden, we don't know...

Is it safe to remove the PBX Delivers Audio option when phones are connected by SBC?

Yes. Yes it is.

 

[cobaltit]

@pitrickzul

No only is it safe, it's recommended. One of the benefits of the SBC is the ability to keep audio between extensions local. Unless you have call recording enabled in which case it will always go through the PBX.

 

[pitrickzul]

Although the SBC actually helped. Whats the point of having a cloud hosted pbx if you need a man in the middle to handle everything?

How do systems like Ringcentral or Broadcloud or whatever cloud pbx work since they have no SBC and are purely cloud systems? Why dont they suffer from the same issues as our stun config?

We used to have a cloud system before and we never encountered these issues, the service was a homemade service so im unaware of how they made it work though... You guys have an idea why?

 

[cobaltit]

You don't need a SBC. A properly configured STUN setup works, it's just a lot of port forwarding, etc. Ring Central has a SBC, it's just at the carrier end, as it is for most providers.