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86 Chapter 7. Linux Virtual Server Overview
Figure 7-1. A Basic LVS Configuration
Service requests arriving at the LVS cluster are addressed to a virtual IP address or VIP.
This is a publicly-routable address 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 server
1
. 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 which connects the LVS router to the
Internet. For instance, if eth0 is connected to the Internet, than 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 router is to redirect service
requests from virtual IP addresses to the real servers. The redirection is based on one of
eight supported load-balancing algorithms described further in Section 7.3 LVS Scheduling
Overview .
1. A virtual server is a service configured to listen on a specific virtual IP. Refer to Section 10.6
VIRTUAL SERVERS
for more on configuring a virtual server using the
Piranha Configuration
Tool
.