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39 | Configuring a Stateful HA Pair
• Power up the primary Dell SonicWALL security appliance,
and then power up the secondary Dell SonicWALL security
appliance.
• Do not make any configuration changes to the primary’s HA
interface; the High Availability configuration in an upcoming
step takes care of this issue. When done, disconnect the
workstation.
Configuring High Availability
The first task in setting up HA after initial setup is configuring
the High Availability > Settings page on the primary Dell
SonicWALL security appliance. Once you configure HA on the
primary Dell SonicWALL security appliance, it communicates
the settings to the secondary Dell SonicWALL security
appliance.
To configure HA on the primary appliance, perform the following
steps:
1. Navigate to the High Availability > Settings page.
2. Select the Enable High Availability checkbox.
3. Under SonicWALL Address Settings, type in the serial
number for the secondary Dell SonicWALL appliance.
You can find the serial number on the bottom of the Dell
SonicWALL security appliance, or in the System > Status
screen of the secondary unit. The serial number for the
primary Dell SonicWALL is automatically populated.
4. Click Apply to retain these settings.
Configuring Advanced HA Settings
1. Navigate to the High Availability > Advanced page.
2. To configure Stateful HA, select Enable Stateful
Synchronization. A dialog box is displayed with
recommended settings for the Heartbeat Interval and
Probe Interval fields. The settings it shows are minimum
recommended values. Lower values may cause
unnecessary failovers, especially when the appliance is
under a heavy load. You can use higher values if your
SonicWALL handles a lot of network traffic. Click OK.
3. To cause the HA pair to change back to the original primary
unit when it becomes available after a failover, select the
Enable Preempt Mode checkbox.
4. To backup the firmware and settings when you upgrade the
firmware version, select Generate/Overwrite Backup
Firmware and Settings When Upgrading Firmware.
5. Select the Enable Virtual MAC checkbox. Virtual MAC
allows the primary and secondary appliances to share a
single MAC address. This greatly simplifies the process of
updating network ARP tables and caches when a failover
occurs. Only the WAN switch that the two appliances are
connected to needs to be notified. All outside devices will
continue to route to the single shared MAC address.
6. Optionally adjust the Heartbeat Interval to control how
often the two units communicate. This timer is the length of
time between status checks. By default this timer is set to
5000 milliseconds, the minimum recommended value is
1000 milliseconds. Using a longer interval will result in the
appliance taking more time to detect when/if failures have
occurred. Less than this may cause unnecessary failovers,
especially when the appliance is under a heavy load.