Specifications

Chapter 1: Overview
12 Equalizer Installation and Administration Guide
Most operating systems allow you to specify a host route (gateway) for packets destined for specific
hosts. If you want your virtual clusters to accept connections from clients on the same network as
the servers, you must configure the servers to route packets destined for these clients through
Equalizer. The clients on the local network must also be configured to use the Equalizer as their
gateway; clients that do not have such routes configured connect to the server’s IP address directly
and not through a virtual cluster (that is, they are not routed through Equalizer).
Using a Second Equalizer as a Backup Unit
You can configure a second Equalizer as a backup unit that will take over in case of failure. This is
known as a hot-backup configuration. The two Equalizers are siblings (or peers), the primary unit
and the backup unit. If the primary Equalizer stops functioning, the backup unit adopts the primary
unit’s IP addresses (clusters) and begins servicing connections. In a failover configuration, the
servers in a virtual cluster use a separate failover alias as their default gateway, rather than the IP
address of the cluster or external port on a particular Equalizer. The failover alias migrates between
the primary and backup unit as needed, automatically ensuring that the servers have a valid gateway
in the event of a failure.
In a hot-backup configuration, both the primary and backup Equalizers are connected to the same
networks; the backup unit’s cluster and external ports must be connected to the same hubs or
switches to which the primary Equalizer’s ports are connected. Figure 9 on page 13 shows a sample
failover configuration.