Installation guide

Setting Up LVS
LVS consists of two basic groups: the LVS routers and the real servers. To prevent a single
point of failure, each groups should contain at least two member systems.
The LVS router group should consist of two identical or very similar systems running Red Hat
Enterprise Linux. One will act as the active LVS router while the other stays in hot standby
mode, so they need to have as close to the same capabilities as possible.
Before choosing and configuring the hardware for the real server group, determine which of the
three LVS topologies to use.
1. The NAT LVS Network
The NAT topology allows for great latitude in utilizing existing hardware, but it is limited in its
ability to handle large loads because all packets going into and coming out of the pool pass
through the LVS router.
Network Layout
The topology for LVS using NAT routing is the easiest to configure from a network layout
perspective because only one access point to the public network is needed. The real
servers pass all requests back through the LVS router so they are on their own private
network.
Hardware
The NAT topology is the most flexible in regards to hardware because the real servers do
not need to be Linux machines to function correctly. In a NAT topology, each real server
only needs one NIC since it will only be responding to the LVS router. The LVS routers, on
the other hand, need two NICs each to route traffic between the two networks. Because this
topology creates a network bottleneck at the LVS router, gigabit Ethernet NICs can be
employed on each LVS router to increase the bandwidth the LVS routers can handle. If
gigabit Ethernet is employed on the LVS routers, any switch connecting the real servers to
the LVS routers must have at least two gigabit Ethernet ports to handle the load efficiently.
Software
Because the NAT topology requires the use of iptables for some configurations, there can
be a fair amount of software configuration outside of Piranha Configuration Tool. In
particular, FTP services and the use of firewall marks requires extra manual configuration of
the LVS routers to route requests properly.
1.1. Configuring Network Interfaces for LVS with NAT
To set up LVS with NAT, you must first configure the network interfaces for the public network
and the private network on the LVS routers. In this example, the LVS routers' public interfaces
(eth0) will be on the 192.168.26/24 network (I know, I know, this is not a routable IP, but let us
pretend there is a firewall in front of the LVS router for good measure) and the private interfaces
Chapter 3.
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