Routing Methods - Red Hat CLUSTER SUITE - FOR RHEL 4 Overview

Chapter 1. Red Hat Cluster Suite Overview 29

1.8.3. Routing Methods

You can use Network Address Translation (NAT) routing or direct routing with LVS. The
following sections briefly describe NAT routing and direct routing with LVS.
1.8.3.1. NAT Routing
Figure 1-22, illustrates LVS using NAT routing to move requests between the Internet and
a private network.
Figure 1-22. 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 the real servers 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 the 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