Skype For Business Onprem - Cant join external parties conferencing/meetings.

Andreas Frank 6 Reputation points


We have a Skype for business on-prem setup with front-end servers in same zone as the users, mediation servers in DMZ-1 and our Edge server in DMZ-2.

When outside of the office (externally) we can connect to meetings/conferencing with external clients and everything is working.
When inside office we can invite external clients to meeting/conferencing, have internal meetings and call/IM internal/external partners. But we can not join external parties meetings. We get the Error 'We could not connect you to video/audio or presentation".

The problems started about 2-3 weeks ago.

Top failure diagnostic codes the last week:


I've looked at all the components and i cant see any traffic being denied from one or the other in the firewall.

I have a CLSlogger file with me trying to join the meeting from Internal and our VPN solution with split tunneling.
Internal doesnt work and VPN works.

Hope you can help me and thanks for any help and suggestions.

Skype for Business
Skype for Business
A Microsoft communications service that provides communications capabilities across presence, instant messaging, audio/video calling, and an online meeting experience that includes audio, video, and web conferencing.
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  1. Sharon Zhao-MSFT 25,051 Reputation points Microsoft Vendor

    @Andreas Frank ,

    It should be a network problem. It recommends you to check the following ports opened for Edge Server external interface: SIP/MTLS/5061 (in/out), RTP/TCP/50000-59999 (out), SIP/TLS 443.

    Meanwhile, you can using Microsoft Remote Connectivity Analyzer to test the setup of your network.

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