The High Availability Config section on the DEVICE | High Availability > Statuspage provides the following information:
HA Mode - Indicates one of:
None – High Availability is not enabled on the unit.
Active/Standby – Active/Standby mode provides basic high availability with the configuration of two identical firewalls as a High Availability Pair. By default, Active/Standby mode is stateless, meaning that network connections and VPN tunnels must be re-established after a failover. To avoid this, Stateful Synchronization can be licensed and enabled with Active/Standby mode.
HA Control Link – Indicates the port, speed, and duplex settings of the HA control link, such as X6 1 Gbps Full Duplex. When High Availability is not enabled, the field displays N/A. The HA control link is used to communicate heartbeats and other control traffic between the units. If the HA control link fails, X0 is used to communicate heartbeats between units; therefore X0 on both units should be in the same broadcast domain.
HA Data Link – Indicates the port, speed, and duplex settings of the HA data link, such as X7 1 Gbps Full Duplex. When High Availability is not enabled, the field displays N/A. The HA data link is used to transfer data necessary to keep settings and firmware synchronized between the units.