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High availability (HA) can be achieved by peering two CNA systems to the same edge routers and configuring the routers to assign different weights to routes asserted by the different CNA systems.
In an HA scenario, one of the devices would be designated as the primary unit and the other as the secondary. Both devices would be configured to receive measurements (both active and passive) and both would operate in route assert mode.
If the weights assigned to the primary unit’s route assertions are slightly higher than the weights assigned to the secondary device’s assertions (and both are higher than any weights assigned to natural BGP routes), the primary unit will always prevail as long as it is functioning correctly.
When the primary unit fails or is removed from service, the routes asserted by the secondary unit should still outweigh the natural BGP routes.
When the primary unit is restored to service, its more heavily weighted routes will once again prevail automatically.
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