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Installing NLB on a Dual-NIC System

You know how to install Network Load Balancing (NLB) on a single-NIC system, but what if you’re running a dual-NIC system? Here are the special configuration considerations for such a setup.

Let’s begin with what you need to have. First, you must have one of the following OSs running in your network:

  • Windows 2000 Advanced Server
  • Win2K Datacenter Server
  • Win2K Server with Microsoft Application Center 2000
  • Windows .NET Enterprise Server

In my examples, I use .NET Enterprise Server beta 2 to build my NLB cluster.

Second, before you begin the dual-NIC configuration, you must have two properly installed Local Area Connections; that is, you should have both interfaces correctly cabled and able to communicate successfully by using TCP/IP. (Verify this communication before proceeding by pinging after hosts on the respective networks.)

To install and configure NLB, right-click My Network Places, then select Properties. The resulting Network Connections dialog box lets you configure the multiple network interfaces for this particular cluster node. You see two network connections. The first connection, called Local Area Connection, is the private interface through which NLB heartbeat messages pass. The second connection, called Local Area Connection 2, will eventually become the public connection. Note that these names are the default names, and you can change them in the initial configuration. Just remember to keep the names straight throughout the configuration. To help you remember which connection is which, I recommend giving each connection a name that more closely represents your scenario. (For example, I named my connections Private Connection and Public Connection, respectively.) Labeling the network greatly facilitates configuration and troubleshooting. (You might even want to go one step further and label the physical network connections with cable tags to indicate which interfaces they attach to.)

To configure the private interface, right-click Local Area Connection, then select Properties. Configure the TCP/IP properties for this network connection, as Web Figure A shows. (Don’t select the Network Load Balancing check box because you don’t want public traffic going to this interface.)

Now, you need to configure the public interface and the cluster. Open the Local Area Connection 2 properties, then select the Network Load Balancing check box and click Properties. In the Network Load Balancing Properties dialog box, click the Cluster Parameters tab. In the Cluster IP configuration area, enter the IP address and subnet mask for the public interface. (The TCP/IP configuration you supply to this connection should be consistent across each node in the cluster.) Then, supply the Fully Qualified Domain Name (FQDN—e.g., and network address to properly handle incoming client requests.

After you’ve supplied the public cluster information, you need to tell the cluster about the configured private interface (i.e., Local Area Connection). You might think that configuring the private IP address on the NLB settings for the public interface is odd, but you’re supplying the same IP address information (i.e., public cluster addresses) to multiple server interfaces. Switch to the Host Parameters tab, then supply the dedicated IP address and subnet mask that you applied to the private interface. If this NLB node is the first one you’re configuring, leave the Priority (unique host identifier) setting at the default value of 1. If this node is a subsequent installation, set the priority value to the next highest unused number.

If this node is the first one in the NLB cluster, you’re finished. Click Apply, then click OK, and your first node is up and running. If this node is a subsequent NLB node, you now have a working cluster. You can use NLB’s command-line operation to verify that the cluster is working correctly. To do so, type

wlbs query

at a command prompt. If your NLB setup is working correctly, you’ll receive a result similar to the one that Web Figure B shows. If not, verify that you’ve configured each public and private interface with the correct TCP/IP settings. Also, ensure that the private interfaces on each node in the cluster can see each other.

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