Red Hat LINUX VIRTUAL SERVER 5.1 - ADMINISTRATION Manual page 18

Chapter 1. Linux Virtual Server Overview
Figure 1.3. LVS Implemented with NAT Routing
In the example, there are two NICs in the active LVS router. The NIC for the Internet has a real
IP address on eth0 and has a floating IP address aliased to eth0:1. The NIC for the private
network interface has a real IP address on eth1 and has a floating IP address aliased to eth1:1.
In the event of failover, the virtual interface facing the Internet and the private facing virtual
interface are taken-over by the backup LVS router simultaneously. All of the real servers located
on the private network use the floating IP for the NAT router as their default route to
communicate with the active LVS router so that their abilities to respond to requests from the
Internet is not impaired.
In this example, the LVS router's public LVS floating IP address and private NAT floating IP
address are aliased to two physical NICs. While it is possible to associate each floating IP
address to its own physical device on the LVS router nodes, having more than two NICs is not a
requirement.
Using this topology, the active LVS router receives the request and routes it to the appropriate
server. The real server then processes the request and returns the packets to the LVS router
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