Dell NSA E8500 Getting Started Manual page 38

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.
7. Set the Probe Interval for the interval in seconds between
communication with upstream or downstream systems.
This timer controls the path monitoring speed. Path
monitoring sends pings to specified IP addresses to
monitor that the network critical path is still reachable. The
default is 20 seconds, and the allowed range is from 5 to
255 seconds. It is recommended that you set the interval
for at least 5 seconds. You can set the Probe IP
Address(es) on the High Availability > Monitoring
screen.
8. In the Probe Count text-field, enter the desired number of
consecutive probes before the appliance considers the
network critical path to be reachable or broken. The
minimum and default is 3 probes, and the maximum is 10.
9. Typically, Dell SonicWALL recommends leaving the
Failover Trigger Level (missed heart beats), Election
Delay Time (seconds), and Dynamic Route Hold-Down
Time fields to their default settings. These fields can be
tuned later as necessary for your specific network
environment.
• The Failover Trigger Level (missed heart beats) timer
is the number of heartbeats the appliance will miss before
failing over. By default, this time is set to 5 missed heart
beats.This timer is linked to the Heartbeat Interval timer –
for example, if you set the Heartbeat Interval to 10
seconds, and the Failover Trigger Level timer to 5, it will
be 50 seconds before the appliance fails over.
Configuring a Stateful HA Pair | 38