When you've made the affinity and port-rule changes, click OK to save your changes. When you receive a warning about adding the new TCP/IP addresses in the TCP/IP configuration, click OK to acknowledge the warning. Now that you've configured NLB, you need to tell the TCP/IP stack what's going on. After the adapters complete the new bindings, the IP Address Properties dialog box will appear. Supply the same configuration information for the VIP address here that you supplied on the Cluster Parameters tab. The static IP address for the first adapter should always be the virtual (i.e., cluster) IP address.
Configuring the TCP/IP Stack
After you've completed the basic TCP/IP information, you need to tell the TCP/IP stack about the host's private, dedicated IP address. In the Internet Protocol (TCP/IP) Properties dialog box, click Advanced. In the Advanced TCP/IP Settings dialog box, enter the private, dedicated IP address and its subnet mask. Don't supply the default gateway for your internal network as an additional default gateway: Using multiple default gateways can create a routing nightmare for your network teams, and providing the internal default gateway could make it easier for intruders to get to your intranet. Instead, you can add the route for the internal network as a static route. The desired result is to leave the default route pointing to the untrusted network. With the stack configured, you've completed the initial NLB configuration.
After the TCP/IP stack has reconfigured itself, you can verify that NLB is installed and working properly. To do so, you can use NLB's command-line operation, which is the same as WLBS's tool. Open a command prompt, then type
C:\> wlbs query
to return the status of the cluster, as known to the current (i.e., local) host. Figure 5 shows typical output from the Wlbs Query command. Other important WLBS and NLB command-line commands include Stop, Start, and Display. You can always type
wlbs
at the command line to get a description of each command and its syntax.
Other Load-Balancing Options
Now that you have a basic understanding of WLBS and NLB, let me throw a wrench in the works. Other load-balancing options exist besides software clustering. You can also use hardware options that take more than just the TCP/IP stack into account.
For example, Cisco System's content-switching solutions (formerly the ArrowPoint product line) and F5 Networks' BIG-IP Controller product line are two products with which I've had some experience. Both products work at the higher-level layers (i.e., from the Network Layer, layer 4, and up) to ensure a balanced solution. The products can also detect unresponsive Web services and take action—a feat that WLBS and NLB currently can't provide. Cisco's solutions and BIG-IP Controller also handle cookies more smoothly. The costs for these products might seem steep initially, but when you consider that you need only a regular server license rather than Microsoft's costly Win2K AS license for each server in your cluster, the price becomes more attractive.
Your specific implementation will determine what kind of load-balancing solution you can run—hardware or software. If you decide on a software solution, you can put together a reliable and effective load-balancing solution by using the basic Microsoft clustering software—NLB and WLBS—to maximize the uptime of your IIS servers.
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