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VVX - One Way Audio on forward

Occasional Advisor

VVX - One Way Audio on forward



I encounter an issue recently and could not find the cause of it.


When calls are placed by polycom VVX300 to another S4B users and the call is forwarded to a mobile phone, sometimes it ends up with one-way audio after 1min.


Here are some details:

- When it happens, I can see that the VVX does not display the call timer at all

- It happens only with the phones, never with the S4B client

- An error about STUN is present in the logs: CIceCheckCandidatePair::SendUseCandidate() # NO STUN request message!

- For the one minute during which the call is fine, I see that traffic goes from phone port (205XX) to Edge (50XXX) and from Edge (3478) to phone (207XX)

- After one minute, audio goes only in direction VVX -> mobile phone


Where should I look for the issue? Mediation server? trunks? Edge? Polycom settings?




Message 1 of 3
Polycom Employee & Community Manager

Re: VVX - One Way Audio on forward

Hello francois,

welcome to the Polycom Community.

It is always useful to include the currently used UC Software version as issues experienced may already be addressed in a newer release.


This also allows yourself and others to check against current software release notes.

The above is also stated in the "Read First"

Therefore the Polycom VoIP FAQ contains this post here:

Question: How can I find out my SIP UC Software Version or the BootROM Version of my Phone?
Resolution: Please check here


There should not be any specific settings enabled on the Phone that I am aware off.


If it fails and you described the call counter does not appear I assume you do not get all the softkeys either which makes me suspect that the signalling including a 200OK from the LYNC / S4B server may not be completed.


You could open a support ticket with MSFT to start with.

Please ensure to provide some feedback if this reply has helped you so other users can profit from your experience.

Best Regards

Steffen Baier

Polycom Global Services

The title Polycom Employee & Community Manager is a community setting and does not reflect my role. I am just a simple volunteer in the community like everybody else. All posts and words are my own & do not represent the views of Employer.


Notice: This community forum is not an official Poly support resource, thus responses from Poly employees, partners, and customers alike are best-effort in attempts to share learned knowledge. If you need immediate and/or official assistance please open a service ticket through your proper support channels.
Please also ensure you always check the VoIP , Video Endpoint , Skype for Business , PSTN or RPM FAQ's
Message 2 of 3
Occasional Contributor

Re: VVX - One Way Audio on forward

Are you using Media ByPass? I encountered a similar problem when using MediaByPass and Refer Support on the Trunk.

Message 3 of 3