Dynamics CRM 2011 Outlook client and load balancing

Let’s assume you are using :

  • Dynamics CRM 2011 farm with 2 (or more) web front ends
  • A load balancer (Microsoft TMG, Citrix Netscaler, Apache, …) to split the load between your Dynamics CRM 2011 front ends
  • The fantastic Outlook Add-in for Microsoft Dynamics CRM 2011

You might face the situation where your CRM installation works fine when you use a web browser but the outlook add-in (or client) does not work properly. It is impossible to connect or configure it through the configuration wizard.

It might be due to the fact that you need to configure your load balancer to use IP based sticky session (opposed to cookie based sessions). The reason for this is very simple, the outlook add-in does not implement any cookies mechanism and the load balancer will simply fail to stick to one specific server. This will result in authentication failures since the outlook client will not “stick” to one specific web front end.

Here are basic steps to configure “IP based sticky sessions” in Microsoft ForeFront TMG:

Step 1: Open ForeFront TMG management console and go to the firewall policies

Step 2: Double click the firewall policy you have setup to expose your multiple CRM web fronts with load balancing

Step 3: In the ”Web Farm” tab, select “Source-IP based” instead of “Cookie based”

Step 4: Click Ok, and apply the modifications. You’ll see that the outlook client will now work correctly.

Side note to conclude : I got ForeFront TMG working smoothly with Microsoft Dynamics CRM 2011 and the outlook add-in as described above by using Source-IP based sessions. We also had the exact same issue with a Citrix Netscaler load balancer and after configuring it with Source-IP based sessions, it worked fine as well !

Hope this will help someone…