Professional Microsoft IIS 8

Network Load Balancing

NLB has already been mentioned in this chapter, but let's take a look at it in more depth now. NLB, sometimes referred to as Network Load Balancing Services (NLBS), was previously Microsoft's solution for load balancing web farms. While it's still supported by Microsoft, it is less often used directly for load balancing and is starting to take on roles like complimenting ARR, as discussed here.

NLB is a type of load balancer that uses its own unique method to balance the load across all the servers. Incoming traffic is routed to all the servers, but only one of them will actually respond to the traffic while the others ignore that traffic. Therefore, it doesn't have any load balancing device in front of the web servers. All the servers work together as peers for a shared cause.

ARR has functionality that far surpasses NLB. That makes ARR a better load-balancing solution, except for one problem. ARR doesn't have its own built-in solution for high availability, so it can't handle failures to the server hosting ARR. As a result, it becomes a single point of failure, completely defeating the purpose of a web farm.

That's where NLB comes in. NLB is a cost-effective, Microsoft-supported solution for high availability, and ARR is a powerful reverse proxy load balancer. Together, they make a strong team.

Let's take a look at what it takes to set up an NLB cluster. One common configuration change that may be needed at the network level is to set static ARP records ...