Installation guide

Chapter 1. Linux Virtual Server Overview
Linux Virtual Server (LVS) is a set of integrated software components for balancing the IP load across a
set of real servers. LVS runs on a pair of equally configured computers: one that is an active LVS router
and one that is a backup LVS router. T he active LVS router serves two roles:
To balance the load across the real servers.
To check the integrity of the services on each real server.
The backup LVS router monitors the active LVS router and takes over from it in case the active LVS
router fails.
This chapter provides an overview of LVS components and functions, and consists of the following
sections:
Section 1.1, “A Basic LVS Configuration”
Section 1.2, “A Three-T ier LVS Configuration”
Section 1.3, “LVS Scheduling Overview”
Section 1.4, “Routing Methods”
Section 1.5, “Persistence and Firewall Marks”
Section 1.6, “LVS — A Block Diagram”
1.1. A Basic LVS Configuration
Figure 1.1, “A Basic LVS Configuration” shows a simple LVS configuration consisting of two layers. On
the first layer are two LVS routers — one active and one backup. Each of the LVS routers has two
network interfaces, one interface on the Internet and one on the private network, enabling them to
regulate traffic between the two networks. For this example the active router is using Network Address
Translation or NAT to direct traffic from the Internet to a variable number of real servers on the second
layer, which in turn provide the necessary services. Therefore, the real servers in this example are
connected to a dedicated private network segment and pass all public traffic back and forth through the
active LVS router. T o the outside world, the servers appears as one entity.
Chapter 1. Linux Virtual Server Overview
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