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One way voice - outbound calls - isolated to ClearOne conference phone

Level 4
Level 4

Hi everyone, 

We are facing weird issue with one way voice that affects only external calls.

No issues with inbound and outband calls while calling internal. 

Issue is not present on cisco IP phones or cisco conference phones.

Issue is isolated to ClearOne conference phone CONVERGE® PRO | VH20

Device configured as Third-party SIP Device (Basic) on the CUCM.

Inbound external calls working fine.

Outbound external calls not working.

If I call 3rd party I can hear them but they cannot hear me. 

Issue escalated with Clearone and they blame trunk configuration.

No issue with any other device that uses the same trunk and also tested with the same extension number (DDI).

Issue has appeared a couple of weeks ago with no changes to the configuration. 

We have single clearone conference phone therefore not able to test with other unit. 

Any suggestions. Please advise.


System version:

Thank you

5 Replies 5

Jonathan Schulenberg
Hall of Fame
Hall of Fame

Have you compared the working and non-working SIP dialogs to see what's different between them? CUBE, or whatever your SIP SBC is, and CUCM will both have detailed logs of this.

Both call flows are using the same cube device. 

For the failed scenario call flow diagram is different it has:






Session Progress

Whereas working case has: Invite Trying Ringing Session Progress



Scott Leport
Level 7
Level 7


If the signaling is working but RTP is not, check your firewall or Internet gateway to ensure that you're allowing the range of RTP ports the conference phone is using.

I have checked and the range range 8000 48198 is already allowed which covers the rtp ports that can be used. Thanks

Almost all one-way audio comes from network-related issues 

so you need to PCAP for the RTP traffic and check if the firewall allowed the audio traffic to pass!?