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Configuring a Stateful HA Pair | 40
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.
•The Election Delay Time can be used to specify an
amount of time the appliance will wait to consider an
interface up and stable before one of them takes the
primary role. This is useful when dealing with switch ports
that have a spanning-tree delay set
•The Dynamic Route Hold-Down Time setting is used
when a failover occurs on a HA pair that is using either
RIP or OSPF dynamic routing. When a failover occurs,
Dynamic Route Hold-Down Time is the number of
seconds the newly-active appliance keeps the dynamic
routes it had previously learned in its route table. During
this time, the newly-active appliance relearns the
dynamic routes in the network. When the Dynamic
Route Hold-Down Time duration expires, it deletes the
old routes and implements the new routes it has learned
from RIP or OSPF. The default value is 45 seconds. In
large or complex networks, a larger value may improve
network stability during a failover.
10. Click the Include Certificates/Keys checkbox to have the
appliances synchronize all certificates and keys.
11. Click Synchronize Settings to synchronize the settings
between the primary and secondary appliances.
12. Click Synchronize Firmware if you previously uploaded
new firmware to your Primary unit while the Secondary unit
was offline, and it is now online and ready to upgrade to the
new firmware. Synchronize Firmware is typically used
after taking your Secondary appliance offline while you test
a new firmware version on the Primary unit before
upgrading both units to it.
13. Click Accept to retain the settings on this screen.