Installation guide

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 which uses
network address translation to replace the address of the real server in the packets with the LVS routers
public VIP address. This process is called IP masquerading because the actual IP addresses of the real
servers is hidden from the requesting clients.
Using this NAT routing, the real servers may be any kind of machine running various operating systems.
The main disadvantage is that the LVS router may become a bottleneck in large cluster deployments
because it must process outgoing as well as incoming requests.
1.4.2. Direct Routing
Building an LVS setup that uses direct routing provides increased performance benefits compared to
other LVS networking topologies. Direct routing allows the real servers to process and route packets
directly to a requesting user rather than passing all outgoing packets through the LVS router. Direct
routing reduces the possibility of network performance issues by relegating the job of the LVS router to
processing incoming packets only.
Figure 1.4 . LVS Implemented with Direct Routing
In the typical direct routing LVS setup, the LVS router receives incoming server requests through the
virtual IP (VIP) and uses a scheduling algorithm to route the request to the real servers. T he real server
processes the request and sends the response directly to the client, bypassing the LVS routers. T his
method of routing allows for scalability in that real servers can be added without the added burden on
the LVS router to route outgoing packets from the real server to the client, which can become a
Chapter 1. Linux Virtual Server Overview
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