Reception attended transfer to internal has no audio but second attempt works fine?

[John14]

Hi Everyone,

So we have 3CX on premises with Reception (Yealink T57W) always receiving calls. When Reception goes to attended transfer to someone within the company, Reception and the other caller have no audio so reception ends the call. When Reception attended transfer the second time right after the call is successfully and both parties can hear each other.

I'm trying to some troubleshooting to see what could cause this issue. PBX delivers audio is enable on both SIP trunks and extensions and Support Re-Invite & Support replaces is disabled on SIP trunk.

If theres any ideas i can try to resolve this issue.

Thanks

 

[AWS2P]

Hi,
PBX and phones are local, same LAN?

Is it a problem on all phones or only one ? is it only with incoming calls?

a transfer with internal call produce same audio problem ?

 

[John14]

Hi,
PBX and phones are local, same LAN?

Is it a problem on all phones or only one ? is it only with incoming calls?

a transfer with internal call produce same audio problem ?

Thanks for the quick reply.

Yes 3CX PBX is on premises and there is 1 deskphone which is local lan and the rest is on softphones.

Seems to happen to 50% of transfers that reception makes to any internal users extensions.

I havent tested to see if this is the same when dialing internally instaed of attended transfer. i will speak with reception and get back to you.

thanks'

 

[AWS2P]

Firewall checker passes green?

No sip ALG?

 

[JohnS_3CX]

Hi @John14

Is the phone auto provisioned on default templates?

How do the softphones reach the PBX? Tunnel over internet or local?

 

[HSGrocer]

I have had a similar issue but with yealink T53W's with attendended transfers over a LAN - When a call is transferred the I hear nothing even when the other party picks up, but the call connects when I hang up.

 

[John14]

Hi @John14

Is the phone auto provisioned on default templates?

How do the softphones reach the PBX? Tunnel over internet or local?

Hi,

Sorry i haven't replied in awhile but i don't think it'll be anything to do with the template as i directly called an extension which is softphone and done an attended transfer to another softphone and it was the same issues. Softphones are local. Firewall check were all good aswell

 

[JohnS_3CX]

Since you have PBX Delivers audio on ext's and trunk, can you run a capture and catch one of those cases?

 

[John14]

Sure i can replicate the issue and will get the capture. I know that we don't send captures through here, Where do i sent this to?

 

[JohnS_3CX]

Don't send them, just take a look at them

You can compare the part that has failed audio VS the part that works.

Does the SDP for example offer codecs that don't exist on both devices? The call will go through but there will be no audio.

 

[John14]

Don't send them, just take a look at them

You can compare the part that has failed audio VS the part that works.

Does the SDP for example offer codecs that don't exist on both devices? The call will go through but there will be no audio.

Hi John,

I have had a look at the captures when replicating these issues. i noticed on the SDP flow that there was a section saying unsupported media type.



I'm guessing this could be the reason. If so, how do i fix this?

Thanks

 

[JohnS_3CX]

Good catch, so who is informing who of the unsupported media type?

What media was offered just before this message?

Are we sure that the phones are configured correctly using the default 3CX templates?

 

[John14]

Good catch, so who is informing who of the unsupported media type?

What media was offered just before this message?

Are we sure that the phones are configured correctly using the default 3CX templates?

Thanks for the reply.

So it looks like its from PBX to the softphone that has the unsupported message.

The media was g711a & U, g7729, g722, gsm and opus.

after ringing i get a 200 OK SDP G711a.