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We have a simple Lync setup with seperate virtual servers for Lync Front End, Lync Edge and we're running a Reverse Proxy. Desktop Clients both internal and external (network wise) are able to log in just fine. Chatting, sending files, sharing screen all works. The only thing that seems to spit errors in the eventlog is the Web Conferencing service on the Front End server:

No connectivity with any of Web Conferencing Edge Servers. External Lync clients cannot use Web Conferencing modality.

Cause: Service may be unavailable or Network connectivity may have been compromised. Resolution: Verify all Web Conferencing Edge Services in the topology are running, and network connectivity is available.

That item in the eventlog is directly preceded by an informational message stating the following:

Connection to the Web Conferencing Edge Server has succeeded

Edge Server Machine FQDN: edgeserver.domainname.nl, Port:8057

The Edge server has no errors in the event log at all and all services are running. I applied every solution I could find which includes:

  • Disabling IPv6 completely on both servers
  • Checking the certificate expiration
  • Assigning both websites in IIS (Internal and External website for IIS) to an IP

The consequences of this problem is that I'm unable to join web conferences with my browser or start a new one through the Desktop client. The desktop client writes this to the event log:

A SIP request made by Lync failed in an unexpected manner (status code 80ef01f7). More information is contained in the following technical data: 503 Service unavailable ms-diagnostics: 3097;reason="No MCU is available via the MCU factory";source="frontendserver.domain.nl";OriginalPresenceState="0";CurrentPresenceState="0";MeInsideUser="Yes";ConversationInitiatedBy="0";SourceNetwork="0";RemotePartyCanDoIM="No"

I really can't find anymore tips on the internet and I can't think of anything else to try. So what am I missing? Does anyone have any pointers for me?

Vincent
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1 Answers1

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Based on your information you shared so far there seamed to be an issue with the Lync Webservices running on the FrontendServer. As we do not know your topology in more details its hard to find the issue with so less information, but I will try to help:

You must have defined a URL for web services (see here for more infos). This should point to your Reverse Proxy (for more infos see here), the reverse proxy should forward the traffic on 443/80 he got to the internal frondend server on 4443/8080 (that depends on your topology). It looks like something isn´t working here. Additional make sure you configured the "Forward the host header" option correctly as explained here.

P.S. For further troubleshooting you can install Fiddler and check which URLs the client try to open and if you see more inside fiddler.

Update:

Just for completeness: There is an change in the may .net Framework which might cause that kind of issue. You can disable this feature or use a proper SSL certificate. More info's can be found here.

BastianW
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