This article explains how NLB algorithm works internally from a technical point of view. This article only applies to Windows NT, Windows 2000 Server, Windows Server 2003 and Windows Server 2008.
General rule for a NLB Cluster which applies to each host in the cluster:
1. All port rules (range) defined in a host cluster must be unique across the cluster.
2. Host priority (Default Host) must be unique across the cluster.
3. Cluster mode must be unique across the cluster: either Unicast or Multicast.
A cluster node maintains a statistical mapping of port rules with associated Virtual IP of the cluster. I will give an port rule example and then explain how it works in cluster when an incoming TCP/IP packet arrives to cluster hosts. I have configured the following port rule at one of the cluster host:
Full Article – http://msmvps.com/blogs/systmprog/archive/2008/02/14/how-network-load-balancing-algorithm-works-internally.aspx
