Owner's Manual

Figure 2. DLF Topology
High Availability (HA)
The active fabric controller (AFC) provides resiliency with minimal or no impact to data traffic using the
high availability (HA) feature. With an HA redundancy model, two controllers (one active, one backup)
work together to ensure data is maintained if a controller is unavailable. The AFC role determination logic
follows the OF specification for switches using multiple controllers. The switch is configured with two
controllers and establishes an OF connection with both controllers.
During installation, you select one controller as the active or primary controller and the other controller
as the standby or secondary controller. However, controller roles are dynamic and are reassigned
automatically, depending on controller availability. The only way to ensure one controller remains active
and the other remains standby is to start the active controller first and wait until it is recognized as the
primary controller before starting the second standby controller. As long as an active controller is not
already present, the first controller recognized by AFC is assigned as the active controller. If an active
controller is present, the other controller is automatically assigned as the standby controller.
An active controller configures forwarding entries in the OF switches. The standby controller does not
receive asynchronous messages, except port status messages, from the OF switches in this mode. When
the HA protocol detects an active controller failure, it reassigns the standby controller as the active
controller without disrupting traffic.
Supported Technologies and Protocols
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