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pair. For example, when the backup SonicWALL takes over for the primary after a failure, an e-mail
alert is sent indicating that the backup has transitioned from Idle to Active. If the primary SonicWALL
subsequently resumes operation after that failure, and Preempt Mode has been enabled, the primary
SonicWALL takes over and another e-mail alert is sent to the administrator indicating that the primary
has preempted the backup.
•
View Log - The SonicWALL also maintains an event log that displays the Hardware Failover events
in addition to other status messages and possible security threats. This log may be viewed with a
browser using the SonicWALL Management Interface or it may be automatically sent to the adminis-
trator's E-mail address. To view the SonicWALL log, click Log on the left side of the management in-
terface.
Forcing Transitions
In some cases, it may be necessary to force a transition from one active SonicWALL to another – for
example, to force the primary SonicWALL to become active again after a failure when Preempt Mode has
not been enabled, or to force the backup SonicWALL to become active in order to do preventive
maintenance on the primary SonicWALL.
To force such a transition, it is necessary to interrupt the heartbeat from the currently active SonicWALL.
This may be accomplished by disconnecting the active SonicWALL's LAN port, by shutting off power on
the currently active unit, or by restarting it from the Web Management Interface. In all of these cases,
heartbeats from the active SonicWALL are interrupted, which forces the currently Idle unit to become
Active.
To restart the active SonicWALL, log into the primary SonicWALL LAN IP Address and click Tools on the
left side of the browser window and then click Restart at the top of the window.
Click Restart SonicWALL, then Yes to confirm the restart. Once the active SonicWALL restarts, the other
SonicWALL in the Hardware Failover pair takes over operation.
Alert!
If the Preempt Mode checkbox has been checked for the primary SonicWALL, the primary unit takes
over operation from the backup unit after the restart is complete.
Configuration Notes
•
If you are configuring the SonicWALL in Transparent Mode on the network, an additional IP address
is necessary for the Hardware Failover configuration.
•
For firmware upgrades, the Primary SonicWALL should be upgraded first. And during the upgrade,
the backup SonicWALL should be disconnected from the LAN or turned off. When the firmware up-
grade is performed on the backup SonicWALL, the Primary SonicWALL should be disconnected from
the network or turned off.
•
Changes made to the backup SonicWALL do not get updated on the Primary SonicWALL until syn-
chronization takes place between the two units.
Hardware Failover Page 141
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