If you are using an Audiocodes SBC to connect your SIP Trunk to Microsoft Teams Direct Routing, you had probably the situation, where inbound calls are failing.
I had this situation a few days ago and spent some time for analyzing it.
SIP Trunk
Missing Music on Hold for PSTN Calls on a Polycom VVX Phone
Some days ago I had a request from a customer about missing Music on Hold on Polycom VVX Phones and an Audiocodes SBC. The customer infrastructure:
- Mixed Lync 2013 and Skype for Business infrastructure on-premises
- Audiocodes Mediant 2600 SBC
- Enterprise SIP Trunk by Deutsche Telekom
- 5.000 Users are enabled for Enterprise Voice features
- Some are using Polycom VVX IP Phone (411 and 601)
- Most users are using the Microsoft Skype for Business Client 2015 or C2R (2016)
The customer reported me, that for PSTN calls by Polycom VVX users the Music on Hold (MoH) was missing. When the same user calls someone in the company, the MoH is played to the other user. So, only PSTN calls are facing this issue. Furthermore, the customer told me that for users with Skype for Business softclient the problem doesn’t exist.
So, in consequence it seems that we have to do a deeper look onto the Polycom VVX configuration because only these users are facing the problem. And only if the call was routed to or from the PSTN.