Load Balancing Exchange 2007 Client Access Servers using Windows Network Load-Balancing Technology – Part 2: Configuring the Windows NLB Cluster

If you missed the other parts in this article series please go to:





In this article we will continue where we left off in part one of this article series on how you load-balance Exchange 2007 Client Access servers using Windows Network Load Balancing technology.


By now you should have a lab environment ready with the servers mentioned in our previous article.


Creating the FQDN for the NLB Cluster in DNS


With the environment up and running, the very first thing you want to do is to create a record for the NLB cluster name in DNS. To do so log on to the domain controller in your Active Directory forest, then open the DNS manager by clicking Start > Run and type dnsmgmt.msc.


Now expand the Forward Lookup Zones container and right-click on the respective forward lookup zone for your Active Directory. On the context menu select New Host (A), then type the name you want to use. As you can see in Figure 2.1, I used MAIL for the purpose of this setup. Then type the IP address you want to use as the Windows NLB cluster IP address (this should be an IP address on the same subnet as the NLB member servers).


Figure 2.1: Creating a DNS Record for the Windows NLB Cluster name in the DNS Manager


Now click Add Host (Figure 2.2) then OK and Done. Close the DNS Manager.


Figure 2.2: Entering the DNS name and IP address


In order for clients on the Internet to connect to the specified Internet name, you must also create a record on the DNS servers hosting your domain. This task is typically done on the DNS servers located at your ISP.


Configuring the Network Settings


Although not necessary (as explained earlier), we will use unicast mode with two network adapters installed in this setup (this gives us the most optimal performance). To configure the second network adapter in each Exchange 2007 Client Access server, open Network Connections and give each LAN connection a meaningful name as shown in Figure 2.3.


Figure 2.3: Naming the Network Connections


Now open the Property page for the NLB LAN adapter, then configure the TCP/IP settings as shown in Figure 2.4. As you can see you should only specify an IP address and a Subnet mask. When ready click OK.


Figure 2.4: Configuring the TCP/IP Settings for the NLB LAN


We now have to change the binding order for the network connections. This is done by clicking Advanced > Advanced Settings in the Network Connections window shown back in Figure 2.3. Under the Adapters and Bindings tab, make sure the Public LAN connection is listed first as shown in Figure 2.5 then click OK.


Figure 2.5: Changing the binding order for the Network Connections


Enabling Network Load Balancing on the First Client Access Server


Okay it is time to enable NLB on the first Client Access server in our setup. This can be done via the property page of the network adapter, or by using the Network Load Balancing Manager. I will enable it via the property page of the network adapter, and then add the second Client Access server to the NLB cluster in the next section. So let us open the property page of the NLB LAN adapter, then check Network Load Balancing as shown in Figure 2.6. With Network Load Balancing selected click the Properties button.


Figure 2.6: Enabling Network Load Balancing


Under the Cluster Parameters tab (Figure 2.7), enter the IP address, subnet mask and full Internet name for the NLB cluster. Next make sure Unicast is selected under Cluster operation mode.


Figure 2.7: Configuring the Cluster Parameters
Now, click the Host Parameters tab and enter the IP address and subnet mask configured for the network adapter (Figure 2.8). Let the other settings stay at default.


Figure 2.8: Configuring the Host Parameters


Click the Port Rules tab then select the default port rule and click Remove.


We now need to add a port rule for each of the ports the NLB cluster should accept client requests on. To do so, click the Add button, then enter the respective port under Port range (Figure 2.9). Also make sure Affinity is set to Single. Finally click OK to add the port rule.


Figure 2.9: Configuring the NLB Cluster Port Rules


Do this for each required port, so you get a list of rules similar to what is shown in Figure 2.10 depending on what client access services you want to allow in your organization.


If you support other types of Internet clients such as POP3 and IMAP4, you would also need to add port 110 and 143 respectively.


Figure 2.10:
List of Configured Port Rules
Click OK and OK again to the Information message you receive (Figure 2.11).


Figure 2.11: Informational dialog box


Now add the new virtual cluster IP address under the TCP/IP property page of the network adapter as shown in Figure 2.12.


Figure 2.12: Adding the NLB Cluster IP Address on the TCP/IP Settings Page


Finally click Add then OK


We have now set up a Windows NLB cluster with one member server.


Adding the Second Client Access Server to the NLB Cluster


What good is a NLB cluster with only one member server? Correct, not very good. So let us add the second Exchange 2007 Client Access server to the cluster as well. To do so open the Network Load Balancing Manager by clicking Start > Run and typing NLBMGR.EXE (or click Administrative Tools > Network Load Balancing Manager). This will open the Network Load Balancing Manager shown in Figure 2.13.


Figure 2.13: Network Load Balancing Manager


To add the second server to the NLB cluster, click Cluster in the menu, then Add Host. In the appearing window, type the name of the second Client Access server then hit Connect (Figure 2.14). Select the respective cluster and click Finish.


Figure 2.14: Adding the Second Client Access Server to the NLB Cluster


Next, type the IP address and subnet mask of the network adapter that should be associated with the NLB cluster then click Finish (Figure 2.15).


Figure 2.15: Configuring the Host Parameter Settings for the Second Client Access Server


Now wait for a little while in order for the server to be added and configured accordingly (Figure 2.16).


Figure 2.16: Second Client Access Server added to the NLB Cluster


Close the Network Load Balancing Manager.


We have now load-balanced the two Client Access servers in our lab environment. But there are still quite a few configuration steps to do, but we will take a look at those in part three of this article series.


If you missed the other parts in this article series please go to:





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