Installation guide

suppose there are three servers in the real server pool. Servers A and B are weighted at 1 and the third,
server C, is weighted at 2. If server C goes down for any reason, servers A and B evenly distributes the
abandoned load. However, once server C comes back online, the LVS router sees it has zero
connections and floods the server with all incoming requests until it is on par with servers A and B.
To prevent this phenomenon, administrators can make the virtual server a quiesce server — anytime a
new real server node comes online, the least-connections table is reset to zero and the LVS router
routes requests as if all the real servers were newly added to the cluster.
1.4. Routing Methods
Red Hat Enterprise Linux uses Network Address Translation or NAT routing for LVS, which allows the
administrator tremendous flexibility when utilizing available hardware and integrating the LVS into an
existing network.
1.4.1. NAT Routing
Figure 1.3, “LVS Implemented with NAT Routing”, illustrates LVS utilizing NAT routing to move requests
between the Internet and a private network.
Figure 1.3. LVS Implemented with NAT Rout ing
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
Red Hat Enterprise Linux 4 Virtual Server Administration
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