Dell SonicWALL GX250 Manual page 158

Note: This IP address is different from the IP address used to contact the SonicWALL
in the General Network settings.
• WAN IP Address (Optional) - This is a unique WAN IP address used to remotely
manage the primary SonicWALL whether it is Active or Idle.
Note: The Synchronize Now button is used for diagnostics and troubleshooting
purposes and is not required for initial configuration.
4. In the Web Management for the primary SonicWALL, configure the backup Son-
icWALL settings as follows:
• Serial Number - Enter the serial number of the backup SonicWALL.
• LAN IP Address - The unique LAN IP address used to access and manage the
backup SonicWALL whether it is Active or Idle.
Note: This IP address is different from the IP address used to contact the
SonicWALL in the General Network settings.
• WAN IP Address(Optional) - This is a unique WAN IP address used to remotely
manage the primary SonicWALL whether it is Active or Idle.
5. Check the Preempt mode checkbox if you want the primary to SonicWALL to
takeover from the backup SonicWALL whenever the primary becomes available
(for example, after recovering from a failure and restarting). If this option is not
used, the backup SonicWALL remains the active SonicWALL.
Note: The primary and backup SonicWALLs use a "heartbeat" signal to communicate
with one another. This heartbeat is sent between the SonicWALLs over the network
segment connected to the LAN ports of the two SonicWALLs. The interruption of this
heartbeat signal triggers the backup SonicWALL to take over operation from the active
unit of the High Availability pair. The time required for the backup SonicWALL to take
over from the active unit depends on the Heartbeat Interval and the Failover
Trigger Level.
6. Enter the Heartbeat Interval time in seconds. Use a value between 3 seconds
and 255 seconds. This interval is the amount of time in seconds that elapses be-
tween heartbeats passed between the two SonicWALLs in the High Availability pair.
7. Enter the Failover Trigger Level in terms of the number of missed heartbeats.
Use a value between 2 and 99 missed heartbeats. When the backup unit detects
this number of consecutive missed heartbeats, the backup SonicWALL takes over
operation from the active unit.
Example: Assume that the Heartbeat Interval and the Failover Trigger Level are
5 seconds and 2 missed heartbeats respectively. Based on these values, the backup
SonicWALL takes over from the active unit after 10 seconds in the event of a failure in
the active unit.
8. Enter the Active SonicWALL Detection Time in seconds using a value between
0 and 300. The default value of 0 is correct in most cases.When a primary Son-
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