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Solved Telekom Sip Trunk (NGN) and Yealink T58A - Outgoing call - 488 Not Acceptable Here

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unibeta

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Good day,

we have a strange problem with a new 3CX installation.
90% of outgoing calls via Telekom are rejected
with the message: 488 Not Acceptable Here
Dialing the same number with the softclient and headset works,
you let the softclient dial the phone in CTI mode it does not work.
Not even if you dial directly via the Yealink T58A.

For a phone that is provisioned via stun-external it works
interestingly, but it doesn't work in the local LAN either.
In stun-external mode, the phone also works in a different mode than directly in the LAN.

We tried a second provider (Placetel), so we can get out without any problems.

Are there known incompatibilities between Yealink and Telekom?
Or can it be a problem because the T58 does not support G711?

Greeting unibeta
 
Hi unibeta,

The end-points are not the issue here I don't believe, I know of lots of Yealink T58's out in the field without having any issues + they are a fully supported IP endpoint with 3CX.

If one provider works fine and another does not, you know where the issue lies.

FYI a 488 Not Acceptable indicates that the session parameters are unacceptable - as you have pointed out this could be down to codecs, but I think on the provider side not the phone despite the fact that a 4xx style response is a client side response.

If you look at this page here it will clarify which the Yealink supports (both G711 a/u are present):
https://www.yealink.com/products_39.html

Have you checked with your provider - a wireshark capture might be useful.
 
Hello @unibeta

Check your activity for a working call and a non working call and check the differences. Also make sure that all calls go out the same outbound rule to ensure that nothing is striped or prepended.
Yealink T58 phones do support G711 so you can add them under the extension settings.
 
Thanks for your feedback.

Under the 3CX's phone provisioning, I can
find only the codecs G722, G729, Opus, PCMU, PCMA.

Nothing else is offered under Add.
 
PCMU = G711 ulaw
PCMA = G711 alaw
 
Oh, thank you, I didn't know that.

If nothing fundamental is known, I will run a trace
to the provider in the hope of getting information there.
 
You could also try disabling E164 settings from the PBX settings and see if that makes any difference although that would affect all calls regardless of location and provisioning method.
 
Just an FYI, some reputable providers have the facility for you to run traces from their platform also - might be worth looking into.
 
E164 is deselected and everything configured according to 3CX specifications for Telekom.
The crazy thing about us is we can do it with the same phone
and the same settings.
Not with our client.
Difference is with the customer VDSL25 and with us VDSL100
from then on there won't be any problems...
 
Here I can tell you the solution if someone has the problem again:

The German Telekom does not support outgoing calls with video function.
Although there is no camera and nothing like that activated the Yealink seems to send a video data/protocol in the outgoing call.
This simply blocks the German Telekom.....
With other providers like Sipgate or Easybell there was no problem.

Ban video calls in the settings of the sip trunk now solved the problem.

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