Thursday, March 31, 2016

NetScaler VPX - load balance Exchange - Part 3 (load balance Outlook - RPC)

After configuring load balancing for SMTP traffic (on port 25), I will now configure load balancing for Outlook (MAPI over RPC). This is what some may now call "legacy outlook" since Outlook connectivity is (primarily) using HTTP in more recent versions of Exchange, notably Exchange 2016. This now applies to "Outlook" in general unlike previous versions of Exchange (2010 and before) where only Outlook Anywhere used HTTP (and OWA of course). 

Note: yes, I am still using Exchange 2010. However, the version of Exchange has little or no effect on general load balancing concepts.

As for the SMTP exercise (see my previous blog post), we need to create (if they are not already created):
  • Servers
  • Services
  • Virtual Servers (with a "VIP")
  • Monitors (optional - there is always a default monitor that checks the status of the (Exchange) servers but not of the services. It is possible that the server is available (functional) but the actual services are stopped. Therefore, we can optionally configure a monitor if we want to fine-tune the awareness of service availability).

We have already created server entries, representing our two Exchange servers, so there is no need to repeat this process. Please refer to my previous blog post if you need to see how to create these entries. So we will create two entries for the RPC service and then a virtual server (with a VIP) to which Outlook clients will be directed. Once again, we can optionally create a custom monitor for the service but for now (to keep matters as simple as possible) I will simply use the default monitor.


As a reminder, here are the server entries that we created in the previous blog post:

Just as we created a service for SMTP, and that we associated with each of the servers (see below), we have to create a service for RPC. Click on "Add":

Note: as mentioned in my previous blog post, we could optionally use a "service group".

I configure a RPC service entry associated with each of the Exchange servers:

Yes, for the protocol and the port, we select "TCP" and "*" respectively.

We now have the following services:

Next, in the virtual server section, we create a "virtual server" (with a virtual - but perfectly functional - IP address) to which Outlook clients will connect. Click on "Add":

Configure the settings as follows (I use the naming convention presented in the Citrix training course referenced in the first post of this blog series. You can use another name of course):

Likewise, use an IP address appropriate for your environment.

Now we need to link (or "bind") the virtual server and the RPC services we created earlier. Click on the link indicated below (... Service Binding):

Click on the arrow indicated by the red dot:

Check the RPC services and click on "Select":

That brings us to the following section where we click on "Bind":

Unlike SMTP load balancing, which does not require persistence, we do need to configure a persistence type for Outlook. Click on "Continue" as shown below:

On the far right side of the screen, we should see a menu with various categories including "Persistence":

Select SOURCEIP as the persistence type (then "OK" and "Done"):

I also want to change the load balancing method to "ROUNDROBIN" so I click on "Method" in the same menu on the right and then "ROUNDROBIN":

Click OK and then Done (above).

We have completed the configuration of load balancing for Outlook (RPC). However, we have to adjust the DNS record for our CAS array so Outlook clients are directed to the Outlook VIP ( on the NetScaler rather than the IP address of the Exchange servers:

Now, on the client machines, the Outlook E-mail AutoConfiguration test shows that Outlook is connecting to the CAS Array - which is now associated with the NetScaler rather than one of the Exchange servers. In fact, without a load balancer that the CAS Array can designate, the CAS Array (essentially an Active Directory logical object) cannot provide effective redundancy or high availability. 

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