Solved Trunk registration to DREI not possible after update to V18u4

[PHSnet]

dear community,
since automatic update of our self-hosted 3cx system (windows) the trunk can not be registered at our provider DREI (Austria).
In the event log the following is written:
"Registration at DREI has failed. Destination (sip:t7.utalk.at:5088;transport=TLS;lr;maddr=62.218.251.58) is not reachable, DNS error resolving FQDN, or service is not available."
The activity log is full of such messages:
"07/18/2022 10:17:18 AM - [CM504005]: Registration failed for: Lc:10000(@DREI[<sip:[email protected]:0/TLS>]); Cause: Cause: 503 Certificate Validation Failure/REGISTER from local"
Certificate seems to be ok. DNS of t7.utalk.at is set statically on local DNS and can be resolved. The provider admitted to have serveral customers with this problem but I'm not sure if it't not also a 3CX problem as the time of the update and date of the lost registration was the same...
Any ideas what I can do?
thanks a lot!

 

[YiannisH_3CX]

Hi @PHSnet

Remove TLS and switch back to UDP as TLS is not supported for the t7.utalk.at registrar. We have tested their new platform that will be supported for TLS but we are waiting the go ahead from Drei to switch our support to that.

 

[PHSnet]

Hi @YiannisH_3CX ,
I suggested that to DREI but unfortunately this is no solution. It seems most (or even all) customers which are using 3CX (or even other systems) with an internet connection not provided by DREI are affected. DREI support is talking about DNS problems which I cannot reproduce nor the root cause is clear to me but at least they seem to feel responsible. I'm still confused because the register fails after update 4. Should I try to downgrade?
br P

 

[YiannisH_3CX]

There are no differences on the way we handle TLS between the 2 versions. The only thing I can suggest is to check our TLS guide and see if something stands out from there: https://www.3cx.com/docs/sip-trunk-tls-srtp/

 

[PHSnet]

Thanks! They fixed it somehow... Now it works again...

 

[YiannisH_3CX]

Glad to see the issue has been resolved.