Configure NLB prerequisites

- [Voiceover] One of my favorite features in a High Availability Network, is the Network Load Balancing feature. In a failover cluster environment the Network Load Balancing feature distributes traffic across several severs, by using TCPIP. By combining two or more computers that are running applications into a single virtual cluster. Network Load Balancing provides reliability and perfomance, for Web servers and other mission critical servers. So let's take a look at this graphic, and we see here three different servers.

Now all three of these servers have the same application installed and they also run failover cluster manager. Now the three different servers also have three different IP addresses. But if we look at the IP addresses at the bottom. We see that all three of these servers, will all respond to the same IP address. They can also reply to the same name. So that way if one or more of the servers, in this cluster go down.

Then the remaining servers will continue to serve up clients. The servers that we just saw in the previous graphic, are called Hosts. And each host runs a separate copy of the server applications. Network Load Balancing distributes incoming client requests across the hosts in the cluster. So you can configure the load that is to be handled by each host. You could also add host dynamically to the clusters, you can add servers anytime.

And that will handle the increased load. Network Load Balancing can also direct all traffic to a designated single host. So if you just want all traffic for a while to go to a single host, this can be done. It's called the Default Host. Network Load Balancing allows all the computers in the clustered, to be addressed by the same set of IP addresses. And it maintains a unique dedicated IP address for each host. For Load Balanced application when a host fails or goes offline.

The load is automatically redistributed among the computers that are still operating. And of course when those computers are ready once again, the offline computers can be transparently rejoined to the cluster, and regain the share of the workload. And that allows the remaining hosts in the cluster to handle less traffic. The're a couple of prerequisites that we need to keep in mind. One is that all hosts must be in the same subnet. In this particular case all our hosts in the 192168.1 Network.

They of course have to all have different host IP addresses two, three, and four. but they all have to start with the same subnet octets. Now there's also no restrictions on adapters, and that means you can have as many adapters as you want, on each of the host computers. In order to get started, we would need to start the failover cluster manager, in each of the servers. And pre-install all of the applications on each of the servers.

After that we create the cluster, and we start the Network Load Balancing Manager. Once we create the cluster we create a cluster IP address for all of the hosts in the cluster to respond to. And then we create a DNS name, that we put the name and the IP address in the DNS server. So now when a client requests files, say from a server. Then they can put in the name of the clustered name or IP address rather than the individual, hosts names or IP addresses.

Either server will respond to the same name or IP addresses, in the DNS database. Using Network Load Balancing in an administrator can greatly increase the redundancy, utilizing multiple servers, in a failover cluster.