Cisco 7604 Configuration Manual page 268

Understanding Failover
Device Initialization and Configuration Synchronization
Configuration synchronization occurs when one or both units in a failover pair boot.
When a unit boots while the peer unit is not available, then both failover groups become active on the
unit regardless of the primary or secondary designation for the failover groups and the unit.
Configuration synchronization does not occur. Some reasons a peer unit may not be available are that
the peer unit is powered down, the peer unit is in a failed state, or the failover link between the units has
not been established.
When a unit boots while the peer unit is active (with both failover groups active on it), the booting unit
contacts the active unit to obtain the running configuration. By default, the failover groups will remain
active on the active unit regardless of the primary or secondary preference of each failover group and
unit designation (unless configured with the preempt command). The failover groups remain active on
the first unit until one of the following occurs:
•
•
•
When both units boot at the same time, the primary unit becomes the active unit. The secondary unit
obtains the running configuration from the primary unit. Once the configuration has been synchronized,
each failover group becomes active on its preferred unit.
If you previously changed the number or size of memory partitions on the primary unit (see the
Note
"Managing Memory for Rules" section on page
configuration, immediately reload the secondary unit so that the memory partitions are the same. During
the initial synchronization, the configuration might not fit properly in the secondary unit memory
partitions, but after reloading, and another configuration synchronization, the secondary unit will be
operational.
Command Replication
After both units are running, commands are replicated from one unit to the other as follows:
•
Note
•
•
Failure to enter the commands on the appropriate unit for command replication to occur will cause the
configurations to become out of synchronization. Those changes may be lost the next time configuration
synchronization occurs.
Catalyst 6500 Series Switch and Cisco 7600 Series Router Firewall Services Module Configuration Guide using ASDM
14-14
A failover condition causes the failover group to become active on the peer unit.
You manually force a failover group to become active on the peer unit using the no failover active
command.
The preempt command forces the failover group to become active on its preferred unit when that
unit becomes available.
Commands entered within a security context are replicated from the unit on which the security
context appears in the active state to the peer unit.
A context is considered in the active state on a unit if the failover group to which it belongs is
in the active state on that unit.
Commands entered in the system execution space are replicated from the unit on which failover
group 1 is in the active state to the unit on which failover group 1 is in the standby state.
Commands entered in the admin context are replicated from the unit on which failover group 1 is in
the active state to the unit on which failover group 1 is in the standby state.
4-11), then after the secondary unit synchronizes the
Chapter 14 Configuring Failover
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