Coyote Point Systems Equalizer, Installation And Administration Manual

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Equalizer Network Configurations
Equalizer Installation and Administration Guide 13
Figure 8 Single network configuration
Most operating systems allow you to specify a network route (gateway) for packets
destined for hosts on the directly attached network, so servers can be configured with host
routes through Equalizer for any machines on the local network that need to be able to
connect to virtual cluster addresses. Machines on the local network that do not have such
routes configured can still connect to the servers directly.
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 referred to as a hot-backup configuration. The two Equalizers, a primary unit and a
backup unit, are referred to as siblings. If the primary Equalizer stops functioning, the
backup unit adopts the IP addresses (clusters) owned by the primary and begins servicing
connections. In a failover configuration, the servers in a virtual cluster use a separate
failover gateway address as their default gateway, rather than using the IP address of the
internal or external interface on a particular Equalizer as their gateway. The failover
gateway address 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 internal and external interfaces must be connected
to the same hubs or switches that the primary Equalizer’s interfaces are connected to.
The Equalizer functioning as the backup unit monitors all traffic to and from the primary
unit and both Equalizers periodically exchange status messages over the local area
network.
Internet
Client
Not Used
Server 1
External Network
199.146.90.0
Equalizer
Client
Server 2 Server 3
Router .1
.10 .11 .12
EXT .1
INT