CHAPTER
TWO
HIGH AVAILABILITY
This document covers configuration of a High Availability cluster using the following features:
• CARP for IP address redundancy
• XMLRPC for configuration synchronization
• pfsync for state table synchronization
With this configuration, two units act as an “active/passive” cluster with the primary node working as the master unit
and the secondary node in a backup role, taking over as needed if the primary node fails.
2.1 High Availability Prerequisites
Before a redundant configuration can be achieved, a few prerequisites must be met.
2.1.1 Assumptions
This guide assumes that:
• Only two cluster nodes are used.
• Both cluster nodes are the same model with identical hardware specs.
• Both units have a factory default configuration and there are no existing settings on these units.
Warning: Do not connect the LAN port of both units into the same LAN switch until some basic settings have
been applied to each node, which will be done by the end of this section. Otherwise there will be an IP address
conflict and communication with each node individually will not be possible until the conflict is resolved.
2.1.2 Determine the Synchronization Interface
One interface on each node will be dedicated for synchronization tasks. This is typically referred to as the “Sync”
interface, and it is used for configuration synchronization and pfsync state synchronization. Any available interface
may be used. It isn’t necessary for it to be a high speed port, but it is necessary to choose the same port on both nodes.
Note: Some call this the “CARP” interface but that is incorrect and very misleading. CARP heartbeats happen on
each interface with a CARP VIP; CARP traffic and failover actions do not utilize the Sync interface.
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