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Chapter 24
Network Load Balancing
Certain versions of the Microsoft Windows operating system allow creation of so called
cluster — a group of hosts which behaves as a single virtual server. Clients’ requests
to the virtual server are distributed to individual computers within the cluster. This
technology is called Network Load Balancing (called NLB in the further text). If WinRoute
and NLB are used, a particular local network can be connected to the Internet by several
independent lines. Network communication will be distributed to these lines in accor-
dance with the corresponding settings (evenly or in dependence on speed of individual
lines, etc.).
The cluster technology provides several benefits, such as increasing of permeability,
response speed and reliability of the Internet connection.
24.1 Basic Information and System Requirements
Creating of a NLB cluster are supported by following operating systems:
• Windows 2000 Advanced Server or Datacenter Server
• Windows Server 2003 Enterprise Edition or Datacenter Edition
To make functionality of the cluster as reliable as possible, it is necessary that the same
operating system is installed at all servers participating.
WinRoute license for a corresponding number of users is needed for each server partici-
pating in the cluster (for details, see chapter 4.6).
Note: The listed versions of the operating systems allow creating of two cluster types:
server clusters and Network Load Balancing cluster. These types cannot be combined.
24.2 Network Configuration
The example describes a cluster configuration where traffic between a local network and
the Internet is divided to two Internet connections (refer to figure 24.1).
Each server needs two network interfaces: one for connection to the local network (usu-
ally, the Ethernet adapter is used) and another for connection to the Internet (e.g. Ether-
net or WiFi). Various types of Internet connections can be used, however, these connec-
tions should be permanent. It is strongly recommended not to use dialed connections!