Enable Network Load Balancing

Applies To: Windows Server 2003, Windows Server 2003 R2, Windows Server 2003 with SP1, Windows Server 2003 with SP2

To enable Network Load Balancing

  1. Open Network Load Balancing Manager.

  2. Right-click Network Load Balancing Clusters, and then click New Cluster.

  3. Enter the cluster's IP address and other cluster information and click Next.

  4. If necessary, add additional virtual IP addresses that will be used by this cluster by clicking Add, entering the virtual IP address and Subnet mask information, then clicking OK. Repeat this process for each additional virtual IP address, then click Next.

  5. If necessary, add appropriate port rules and then click Next.

  6. Type the name of a host that will be a member of your cluster and click Connect. After you click Connect the network adapters that are available on the host that you typed will be listed at the bottom of the dialog box. Click the network adapter that you want to use for Network Load Balancing and then click Next. The IP address configured on this network adapter will be the dedicated IP address for this host.


    • To start Network Load Balancing Manager, open a Command prompt. From the command window, type NLBMgr, and then press ENTER.
  7. Configure the remaining host parameters as appropriate, then click Finish.

  8. Add additional hosts as appropriate.


  • To ensure that Network Load Balancing Manager is displaying the most recent host information, right-click the cluster and click Refresh. This step is necessary because the host properties that Network Load Balancing Manager displays are a copy of the host properties that were configured the last time Network Load Balancing Manager connected to that host. When you click Refresh, Network Load Balancing Manager reconnects to the cluster and displays updated information.


  • When using Network Load Balancing Manager, you must be a member of the Administrators group on the host that you are configuring, or you must have been delegated the appropriate authority. As a security best practice, consider using Run as to perform this procedure. If you are configuring a cluster or host by running Network Load Balancing Manager from a computer that is not part of the cluster, you do not need to be a member of the Administrators group on that computer. For more information, see Default local groups, Default groups, and Using Run as.

  • To start Network Load Balancing Manager, open a Command prompt. From the command window, type NLBMgr, and then press ENTER.

  • If Network Load Balancing Manager is not used to enable Network Load Balancing, you must manually add the cluster's IP address to the TCP/IP settings on each host. For more information, see "Set up TCP/IP for Network Load Balancing" in Related Topics below.

  • To install and configure Network Load Balancing, you must use an account that is in the Administrators group on each host. As you install and configure each host, if you are not using an account in the Administrators group, you will be prompted to provide the logon credentials for such an account. You can set up an account that Network Load Balancing Manager will use by default by clicking Credentials in the Network Load Balancing Manager Options menu. It is recommended that this account is an account not used for any other purpose. Be sure to keep the password from expiring on the account (follow your organization's policies for password renewal).

  • When you add additional hosts, they will automatically inherit the cluster port rules from the initial host.

  • If Network Load Balancing clients are accessing a cluster through a router, be sure that the router meets the following requirements:

    • Accepts a dynamic Address Resolution Protocol (ARP) reply that maps the unicast IP address to its unicast media access control (MAC) address

    • In multicast mode, accepts an ARP reply that has a MAC address in the payload of the ARP structure. If your router does not meet these requirements, you can also create a static ARP entry in the router. Certain routers require a static ARP entry because they do not support the resolution of unicast IP addresses to multicast MAC addresses.

  • The parameters set in this procedure are recorded in the registry on each host.

  • Network Load Balancing also supports unattended setup. For information about unattended setup, see "Planning for unattended setup" in Related Topics.

  • When installing Network Load Balancing, you might expect to find a setup application (such as Setup.exe). There is no such application. The Network Load Balancing driver is installed as a standard Windows networking driver.

Information about functional differences

  • Your server might function differently based on the version and edition of the operating system that is installed, your account permissions, and your menu settings. For more information, see Viewing Help on the Web.

See Also


Connect to existing clusters from Network Load Balancing Manager using a host list
Checklist: Enabling and configuring Network Load Balancing
Virtual clusters
Create a new port rule
Configure cluster parameters
Configure host parameters
Configure Port Rules
Set up TCP/IP for Network Load Balancing
Network Load Balancing parameters
Planning for unattended Setup