Using OCS 2007 R2 CWA with Lync Server 2010

At this time, there are going to be a few scenarios where you may need to deploy the R2 version of Communicator Web Access with Lync Server 2010. The core reason here, is that the RTM Version of Lync Server 2010 contains a feature on the front end called Lync Web App. Eventually, Lync Web App will become a full featured web client, however, today it is only used for users to join online meetings from the web. There is no ability to access Lync Web App from a URL and sign-in, or use it as a instant messaging too. This is planned to be released SP1 of the product, that timeframe is unknown right now.

To fill this gap, customers will have to deploy the OCS 2007 R2 CWA role, which can register against a Lync Server 2010 Pool. This post will show you how to configure OCS 2007 R2 CWA to work in your Lync Server 2010 environment.


Preparing the Environment

The most important piece of information in this blog, is that the Schema Prep for OCS 2007 R2 must be run in the environment before the Lync Server 2010 Schema Prep, or you will not be able to install the R2 version of CWA. If this is a deployment where there have not been prior installs of OCS 2007 R2, you will need to obtain this media, and run that Schema Prep before your Lync deployment starts, so it is very important to plan for this in your design/planning phase of your project.

Also, to get straight to the point for this blog, I am going to assume you have prepared the schema in the correct order, have your Lync Server 2010 environment online, and have already installed the CWA Role on a server. I will walk through creating the virtual directory, as well as integrating it with your Lync environment.

Use this Deployment Guide to install and configure the CWA role

Creating the OCS 2007 R2 Virtual Web Server

One you have the CWA role installed, and a valid certificate installed on the server, you must configure the virtual web server that clients will access.

I will walk you through the process for creating an External web server, however the same process applies for the Internal web server. The difference being the types of authentication allowed, external allows forms, where as internal also allows NTLM authentication.

Login to your R2 CWA server, and open the Communicator Web Access Admin Console


Once in the admin console, right click on your server and choose Create Virtual Web Server


Navigate through the setup wizard, choose only your Web Server Type, in my case I am choosing External. Make sure to select a valid HTTPS certificate when prompted.

When you get to this section, Specify IP Address and Port it is important to note that this is the IP and listening port for your web server, not the communication between Lync and your CWA server, we will get to that next.


After entering a description for your virtual web server, the most important part of this wizard is the Specify a Listening Port section. This port defines what this application will listen on, and communicate with your Lync front end on. Because of the change in ports between OCS R2 and Lync, previously used values like 5070, or 5071 as you will see in older blog posts of mine do not work. You must pick a port that is not being used by an application currently. For my example I am using 4790.This can be any port, as long as your Lync front end and this server can communicate on that port.


Next, define your next hop pool, choose the appropriate Lync pool as your next hop and leave the port to default 5061.


Complete the wizard and start the virtual server.

Your settings should look similar to this


Now that you have completed this, you will need to make Lync aware of this server.

As you will find in the OCS 2007 R2 to Lync Server 2010 Migration Guide, you must merge your Legacy (OCS 2007 R2 components in to your Lync Topology.

Configuring Lync Server 2010

Now that we have our CWA server configured, we must make the Lync topology aware of this server. To do so, we will merge the legacy topology in to our Lync topology. This is possible through PowerShell using the Merge-CSLegacyTopology cmdlet, however I will be using the GUI.

Before completing this task, you must install the OCS WMI Backwards Compatibility tool, this can be found on the install media, called ocswmibc.msi

First, navigate to your Lync front end and open the Topology Builder.

If you already have coexistence with a R2 environment you will be very familiar with this process, and you will also see the BackCompatSite listed.


Right click where it says Lync Server 2010 and choose Merge 2007 or 2007 R2 Topology


In this post, I am assuming there are no R2 pools, and we are just importing the CWA server and web site. Because of that, you will actually leave the wizard blank when it asks for servers. This wizard will connect to servers in your environment and pull configuration data out of WMI, and input them into this BackCompatSite that will reside on the CMS. This is the major change from OCS 2007 R2 to Lync, is what used to be in WMI, is now in the CMS. You can find plenty of resources to get into more detail about that on Nexthop.




Verify the setting selected in the wizard, and choose Next to merge your legacy topology.

Everything should complete, choose Finish and you will now see your new site.


Expand BackCompatSite and expand TrustedApplicationServers for this blog post, we are concerned only with the trusted application servers, this is where your CWA, and other R2 server roles like group chat will appear.


Once you have verified that your R2 CWA server appears correctly, right click where it says Lync Server 2010 and choose Publish Topology.



Once you have published your topology, we will have one last step to verify our web server was imported correctly.

Open the Lync Server Management Shell and run the following command: Get-CSTrustedApplication

This command will return trusted applications that are associated with Trusted Application Servers and Trusted Application Pools in your environment, you may have many depending on your topology. However the two we are looking for, involve CWA.

Your output should return something similar to below:


I have crossed out my server names, however there should be the FQDN of your CWA server where I have marked.

The two entries represent the external facing web site that users hit, as well as the port that is used to communicate with the Lync front end, as you can see highlighted below, the port you assigned should be listed there.


You should now be able to login to CWA as a Lync Server 2010 user! If you run into issues, make sure to check out this blog relating to the SPN error related to CWA service accounts in R2.

Also, make sure that your CWA server is on the latest release of OCS 2007 R2 patches which can be found here:


I hope this helps you extend CWA capability to your Lync users, if you have any issues please contact me via the comments and I will try to help you the best I can.


About Randy Wintle

Unified Communications Architect

Posted on November 18, 2010, in CWA, Lync, Lync RC, Microsoft, OCS, OCS 2007 R2, Reach Client, Unified Communications. Bookmark the permalink. 19 Comments.

  1. Has anyone installed CWA 2007 R2 on a Server 2008 R2 box and had it work yet? I tried a while ago, but CWA R2 wasn’t compatible with 2008 R2 – a patch was supposed to be released, but I don’t think it ever was. I can only get one-way communication through CWA. CWA external to Lync internal works fine, Lync Internal to CWA external IM’s won’t go through.

    I love how this is the only method to get external communication working wiht Lync 2010 and it doesn’t work on 2008 R2 servers.

  2. Hi,

    Would you know what policies affect Lync-enabled users using CWA? Is it the Lync ClientPolicies or the OCS .adm GPO policies?


  3. Hi Randy,

    I tried to use desktop sharing in the CWA client. I have put down the firewall in CWA, and I have also installed CWAPlugin in the client user.

    When I click Share Desktop, it says
    “The Communicator Web Access Plug-in has been successfully loaded.”
    and then after a while it will say
    “Cannot start desktop sharing session currently.”
    The other user doesn’t even see that a Share Desktop has been initiated.

    I have also edited the OCS GPO default policy to enable Web Conferencing and Desktop Sharing; but still desktop sharing does not work.

    Any ideas on what I’m missing out?

    Help is appreciated.

    Thank you very very much.

    • Is the 50K range open on your firewall?

      Do you have and published and on the certificate?

      Any anti virus that could be blocking this on the desktop side as well?

  4. ambati.VenkataRamana

    It was very good article .

    Thanks a lot

  5. Great article. If the environment never had OCS/OCSR2 and the schema was only prepped for Lync, can it be prepped for OCSR2 and re-prepped for Lync? Thanks.

    • Randy Wintle

      No, you must prep for OCS or OCS R2 before Lync. Once the Lync Prep has been completed, unless you restore from an AD Backup, you cannot prep for R2/R1 of OCS.

  6. Thank you! This article was very helpful.

  7. Robert Wagner

    I did not extend my schema before installing Lync, your notes idicate you cannot use the R2 version if you do not extend the schema for Office communicator first. Can you still use the Standard version OCS 2007 if you installed Lync first?

    I am trying to run iDialog the iphone client for Lync. From the support manual:
    “Microsoft OCS 2007, 2007 R2, or Lync 2010 server system that is properly configured, including an OCS Communicator Web Access (CWA) Server. Both CWA 2007 and CWA 2007 R2 are supported.”

    So my question is can I install CWA 2007 even thought I did not extend the schema for OCS before installing Lync.

    • Unfortunately you must extend the schema for prior versions before extending for Lync if you want to use prior version roles.

      So in your case you cannot install a 2007 server as the schema was never prepped for 2007.

  8. I noticed the call forwarding feature is no longer available when users are on the Lync pool. Is there a way to get this to work again?

    • When you are using the OC 2007 R2 client against a Lync back end, you lose certain features like call control.

      You must upgrade to the lync client to regain these features.

  9. I would like to note something, that should be taken into consideration, you have to make sure that your lync topology support only the default sip domain that was supported with OCS 2007 R2 prior merging the toplogy otherwise you will not be able to merge it.

    thank you for the good post

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