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Get IT Done: Configuring network load balancing in Windows 2000

Get a big picture look at how to use load balancing to make your servers more efficient.


In the Daily Drill Down “Understanding Windows 2000 network load balancing,� I showed you what network load balancing is and how it could benefit your network. But how do you make it work? In this Daily Feature, I’ll show you how to make it work for both Windows 2000 and Exchange 2000.

Configuring Windows 2000 for load balancing
Network load balancing installs by default when you install Windows 2000 Advanced Server or Datacenter Server. All you need to do to get your hosts up and running is configure network load balancing on the appropriate interface.

After you install the network hardware and Windows 2000 Advanced Server or Datacenter Server, boot the server and open the Network And Dial-Up Connections folder. Right-click the network interface on which you want to configure network load balancing and choose Properties. Configure the TCP/IP protocol with the dedicated IP address, appropriate subnet mask, and other TCP/IP properties for the interface.

Next, select Network Load Balancing from the Components list and then click Properties. Windows 2000 will display a Network Load Balancing Properties sheet with three tabs: Cluster Parameters, Host Parameters, and Port Rules.

The Cluster Parameters tab lets you specify the dedicated IP address for the interface, the primary IP address, and related parameters. The options on the Cluster Parameters page are:
  • ·        Primary IP Address—This is the cluster IP address and the virtual address that clients will use to request services from the cluster. You must publish this address in DNS for the respective services.
  • ·        Subnet Mask—For this option, specify the subnet mask for the primary IP address according to the network segment on which the cluster resides.
  • ·        Full Internet Name—Specify a fully qualified domain name (FQDN) for the cluster, such as cluster.techrepublic.com for this option. This FQDN should be the same for all hosts in the cluster. It must resolve to the primary IP address through DNS (or through a hosts file entry). If you are only hosting one service, you can use that host name for the cluster. For a cluster exclusively for the techrepublic.com Web site, for example, you might use www.techrepublic.com for this field.
  • ·        Network Address—This read-only parameter displays the interface’s MAC address.
  • ·        Multicast Support—Select this option to use multicast rather than unicast addressing.
  • ·        Remote Password And Confirm Password—For this option, specify a password to protect remote access to this cluster host (see following item).
  • ·        Remote Control—Windows 2000 includes an application, Wlbs.exe, that you can use to control hosts in a cluster. Select this option to allow the host to be remotely managed and specify a password in the two password fields. Wlbs.exe is a console-based program, so you can use it from a command console interactively or incorporate it into scripts.

You use the Host Parameters tab of the Network Load Balancing property sheet to specify the dedicated IP address for the Interface, the Initial Cluster State, and the Host Priority Number. The dedicated IP address and subnet mask default to the address and subnet mask assigned to the network adapter through its TCP/IP properties. The Initial Cluster State determines whether or not the server starts up as a member of the cluster automatically when the server boots. By default, this setting is selected, but you can deselect it to have the server boot without becoming a member of the cluster. You can then use the Wlbs.exe application to join the server to the cluster. The Host Priority Number determines which host becomes the default host if the current default host goes offline. If you don’t specify a unique host number here, the host will not be allowed to join the cluster.

The Port Rules tab lets you create rules that determine client affinity based on the port and protocol type. You can configure different client affinities for different ports and protocol types, although the port ranges for a given protocol type cannot overlap in two different rules. To create a rule, first select the port range and protocol type. Then, if you want multiple hosts to handle traffic for the port and protocol type specified by the rule, select Multiple Hosts and then select the type of affinity (None, Single, or Class C). Use the Load Weight value to specify the percentage of load that the current server should handle or select Equal to have network load balancing distribute the load equally.

If you want to have only a single host in the cluster handle traffic for a specific port/protocol range, select the Single Host option. Then, specify the host’s priority for the traffic using the Handling Priority control. The host with the lowest Handling Priority value for traffic that applies to the rule will handle the traffic unless that host goes offline. If it does go offline, the cluster host with the next highest priority will handle the traffic. All hosts must have a unique Handling Priority value.

You can use the Disabled option to specify that all traffic for the specified port/protocol range be discarded rather than processed. This, in effect, allows you to create a minifirewall to restrict traffic for the port(s) and protocol(s) defined for the rule.

After you’ve configured the settings for network load balancing and defined the necessary port rules, click OK to close the property sheet and then click OK to close the Network Interface property sheet. If you configured the host to start in the cluster immediately, it will add itself to the cluster. Otherwise, use Wlbs.exe to add the host to the cluster when you’re ready to bring it online.

Configuring network load balancing support in Exchange 2000
Exchange 2000 can also benefit from network load balancing. However, to make Exchange 2000 aware that network load balancing is in place, you must do one other thing beyond turning it on in Windows 2000. Open Exchange System Manager, right-click the server object, and select Properties. When the Properties window appears, make sure you’re on the General tab.

For servers that are going to act as front-end servers, you must select the This Is A Front-End Server check box. Close System Manager and dismount and remove the mailbox and public folder stores. Restart your server, and you’re done.

Conclusion
Network load balancing can be a big benefit to your network. However, you need to know how to enable the feature. Fortunately, Microsoft made it relatively simple to take advantage of this feature once you know where to find it.

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