Lync Server Centralized Logging Service Agent Service could not be started

Just a quick article to highlight an issue I had recently.

Fresh install of Lync Server 2013, updates applied via WSUS (everything was approved) and the latest Lync Server Cumlative Update (September 2014) had been applied.

Lync Topology was configured, front end server brought online. Everything looked ok, Topology tab in LSCP showed green status, and a nice green tick under replication.

CMS-Error-Topology-greenI confirmed the service was actually running.


But I spotted an error with the Central Logging Agent in Event Viewer.


A quick search showed up the following KB2986072 with as a Known Issue


After you install this security update on a system that is running Microsoft Lync Server 2013, you find that the Central Logging Service is not listening on designated ports. This causes the Central Logging Service not to start or capture data. When the problem occurs, an exception error message that resembles the following is logged in the event log:

Lync Server Centralized Logging Service Agent Service could not be started.
Source: LS Centralized Logging Agent
Event ID: 33005
Exception: Could not load file or assembly ‘Microsoft.Rtc.ClsAgent.IISLog, Version=, Culture=neutral, PublicKeyToken=31bf3856ad364e35′ or one of its dependencies. The system cannot find the file specified.
Exception type: FileNotFoundException
Additional Data:
Source: ClsAgent
Stack Tracer.Trace:
at Microsoft.Rtc.ClsAgent.AgentCore.InitializeAgentCore()
at Microsoft.Rtc.ClsAgent.ClsAgent..ctor(ClsAgentService service)
at Microsoft.Rtc.ClsAgent.ClsAgentService.StartAgent()
at Microsoft.Rtc.ClsAgent.ClsAgentService.OnStart(String[] args)
Data: 0 key/value pairs
Inner Exception:
Cause: Exception during startup
Check the events prior to this to resolve the service startup issue.


This problem can occur if you install this security update on Lync Server 2013 before you install the August Update of Lync Server 2013.



  • If you do not have August 2014 Update installed already, install OCSCore.msp from the August 2014 Update, and then reinstall the following security update:
    DownloadDownload the OCSCore.msp package now.
  • If you already installed this security update without first installing August 2014 Update, you must uninstall this security update, install August 2014 Update, and then reinstall this security update.

And that worked for me.

A little strange that a server which has been fully updated prior to being deployed would have an error like this. A cumlative update is supposed to be just that, cummlative. Having to install a previous one is a bit dissapointing…  But at least it’s easy enough to fix.

Thanks for reading.

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About Graham Cropley

Working as a Senior Consultant for Skype for Business, Exchange, and Office 365.

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