Installation guide

topologies. While the LVS router needs to be running Red Hat Enterprise Linux to process

the incoming requests and perform load-balancing for the real servers, the real servers do

not need to be Linux machines to function correctly. The LVS routers need one or two NICs

each (depending on if there is a back-up router). You can use two NICs for ease of

configuration and to distinctly separate traffic — incoming requests are handled by one NIC

and routed packets to real servers on the other.

Since the real servers bypass the LVS router and send outgoing packets directly to a client,

a gateway to the Internet is required. For maximum performance and availability, each real

server can be connected to its own separate gateway which has its own dedicated

connection to the carrier network to which the client is connected (such as the Internet or an

intranet).

Software

There is some configuration outside of Piranha Configuration Tool that needs to be done,

especially for administrators facing ARP issues when using LVS via direct routing. Refer to

Section 2.1, “Direct Routing and arptables_jf” or Section 2.2, “Direct Routing and

iptables” for more information.

2.1. Direct Routing and arptables_jf

In order to configure direct routing using arptables_jf, each real server must have their virtual

IP address configured, so they can directly route packets. ARP requests for the VIP are ignored

entirely by the real servers, and any ARP packets that might otherwise be sent containing the

VIPs are mangled to contain the real server's IP instead of the VIPs.

Using the arptables_jf method, applications may bind to each individual VIP or port that the

real server is servicing. For example, the arptables_jf method allows multiple instances of

Apache HTTP Server to be running bound explicitly to different VIPs on the system. There are

also significant performance advantages to using arptables_jf over the iptables option.

However, using the arptables_jf method, VIPs can not be configured to start on boot using

standard Red Hat Enterprise Linux system configuration tools.

To configure each real server to ignore ARP requests for each virtual IP addresses, perform the

following steps:

1. Create the ARP table entries for each virtual IP address on each real server (the real_ip is

the IP the director uses to communicate with the real server; often this is the IP bound to

eth0):

arptables -A IN -d <virtual_ip> -j DROP

arptables -A OUT -d <virtual_ip> -j mangle --mangle-ip-s <real_ip>

This will cause the real servers to ignore all ARP requests for the virtual IP addresses, and

change any outgoing ARP responses which might otherwise contain the virtual IP so that

Direct Routing and arptables_jf