Ring Group SBC Extensions issue

[amenee]

Hi all,

My client's 3CX has been set with a simple ring group made of 5xExtensions - 4xExtensions are behind an SBC while the other Extension is STUN remote wfh.

They reported an issue where the 4xExtensions behind the SBC didn't ring at all while the remote STUN Extension rang.

I've further investigated this issue and I seem to have found some logs that could point me to identifying the issue 'though I'm not sure I'm looking in the right place.

More specifically, I suspect that the issue is documented by the below log entries (edited for privacy purposes):
09/29/2020 1:03:50 PM - [CM503003]: Call(C:471): Call to <sip:[email protected]:0> has failed; Cause: 487 Request Terminated/INVITE from 127.0.0.1:5080
09/29/2020 1:03:50 PM - [CM503003]: Call(C:471): Call to <sip:[email protected]:0> has failed; Cause: 487 Request Cancelled/INVITE from 127.0.0.1:5080
09/29/2020 1:01:00 PM - [CM503003]: Call(C:470): Call to <sip:[email protected]:0> has failed; Cause: 487 Request Terminated/INVITE from 127.0.0.1:5080
09/29/2020 1:01:00 PM - [CM503003]: Call(C:470): Call to <sip:[email protected]:0> has failed; Cause: 487 Request Cancelled/INVITE from 1.1.1.1:4036
09/29/2020 1:00:13 PM - Call to T:RingAll:800@[Dev:sip:[email protected]:5060,Dev:sip:[email protected]:5060;rinstance=1-fe3fa949255142c0a393006cf5739b90,Dev:sip:[email protected]:4036] from L:470.1[Line:10001<<0404807261] failed, cause: Cause: 503 Remote end of tunnel is not connected/INVITE from 127.0.0.1:5080
09/29/2020 1:00:13 PM - [CM503003]: Call(C:470): Call to <sip:[email protected]:0> has failed; Cause: 503 Remote end of tunnel is not connected/INVITE from 127.0.0.1:5080
09/29/2020 1:00:13 PM - Call to T:RingAll:800@[Dev:sip:[email protected]:5060,Dev:sip:[email protected]:5060,Dev:sip:[email protected]:5060;rinstance=1-fe3fa949255142c0a393006cf5739b90,Dev:sip:[email protected]:4036] from L:470.1[Line:10001<<0404807261] failed, cause: Cause: 503 Remote end of tunnel is not connected/INVITE from 127.0.0.1:5080
09/29/2020 1:00:13 PM - [CM503003]: Call(C:470): Call to <sip:[email protected]:0> has failed; Cause: 503 Remote end of tunnel is not connected/INVITE from 127.0.0.1:5080
09/29/2020 1:00:13 PM - Call to T:RingAll:800@[Dev:sip:[email protected]:5060,Dev:sip:[email protected]:5060,Dev:sip:[email protected]:5060,Dev:sip:[email protected]:5060;rinstance=1-fe3fa949255142c0a393006cf5739b90,Dev:sip:[email protected]:4036] from L:470.1[Line:10001<<0404807261] failed, cause: Cause: 503 Remote end of tunnel is not connected/INVITE from 127.0.0.1:5080
09/29/2020 1:00:13 PM - [CM503003]: Call(C:470): Call to <sip:[email protected]:0> has failed; Cause: 503 Remote end of tunnel is not connected/INVITE from 127.0.0.1:5080
09/29/2020 1:00:13 PM - Call to T:RingAll:800@[Dev:sip:[email protected]:5060,Dev:sip:[email protected]:5060,Dev:sip:[email protected]:5060,Dev:sip:[email protected]:5060,Dev:sip:[email protected]:5060;rinstance=1-fe3fa949255142c0a393006cf5739b90,Dev:sip:[email protected]:4036] from L:470.1[Line:10001<<0404807261] failed, cause: Cause: 503 Remote end of tunnel is not connected/INVITE from 127.0.0.1:5080
09/29/2020 1:00:13 PM - [CM503003]: Call(C:470): Call to <sip:[email protected]:0> has failed; Cause: 503 Remote end of tunnel is not connected/INVITE from 127.0.0.1:5080

 

[JohnS_3CX]

so all 5x in total are in the same ring group, what ring strategy do you use and was the STUN extension on the top of the list?

 

[amenee]

The ring strategy is RingAll and the STUN extension is at the bottom of the list.

 

[JohnS_3CX]

From your error message, it would appear that the tunnel was interrupted during the time of this call.

This means the SBC cannot be reached so all the 4x phones behind it will not ring.

I would suspect the network connection (SBC LAN, or the site's WAN) if this was a momentary interruption.

 

[amenee]

Hi John and thank you for your reply.

I've now checked both the LAN and the site's WAN and they both seem operating as normal (no WAN disconnections reported by the router's logs).

Any other ideas on what else could've caused the SBC to disconnect?

Guess I'm going to have to check the SBC logs if that recurs (set SBC logging to medium now).

 

[JohnS_3CX]

Normally the SBC should remain online 24/7 with the only exception being if you manually update it.
And even then, the update takes less than a minute, it's pretty fast.

Reasons for disconnections can be some of the following:

- SBC machine overloaded (should never be the case if you have a dedicated SBC machine)
- The LAN cabling or local network is down
- The WAN of the SBC is facing trouble (overloaded or facing disconnections)
- The WAN of the PBX was facing trouble, causing the remote SBC to also disconnect

This is just speculation mind you, but it can happen. Best to monitor the situation and if it happens often you will have to take a closer look at the remote site.

 

[JohnS_3CX]

If you continue to face the issue, here are some key questions to answer:

- does this happen all the time when calls reach the ring group or only sometimes?
- do you have BLFs on the SBC phones? (how many in total)
- try to switch to TCP and see if this makes a difference (SIP Trunks>SBC Settings> Security)

 

[JohnS_3CX]

You can also try to update your SBC to 16.2.24 which is our latest beta and a close release candidate.