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A virtual server is a service configured to listen on a specific virtual IP.

Figure 1.20. Two-Tier LVS Topology

Service requests arriving at an LVS router are addressed to a virtual IP address or VIP. This is a

publicly-routable address that the administrator of the site associates with a fully-qualified

domain name, such as www.example.com, and which is assigned to one or more virtual

servers1. Note that a VIP address migrates from one LVS router to the other during a failover,

thus maintaining a presence at that IP address, also known as floating IP addresses.

VIP addresses may be aliased to the same device that connects the LVS router to the public

network. For instance, if eth0 is connected to the Internet, then multiple virtual servers can be

aliased to eth0:1. Alternatively, each virtual server can be associated with a separate device

per service. For example, HTTP traffic can be handled on eth0:1, and FTP traffic can be

handled on eth0:2.

Only one LVS router is active at a time. The role of the active LVS router is to redirect service

requests from virtual IP addresses to the real servers. The redirection is based on one of eight

load-balancing algorithms:

Two-Tier LVS Topology

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Red Hat CLUSTER SUITE FOR ENTERPRISE LINUX 5.2 Guía de instalación Pagina 37