Cisco ASA 5505 Configuration Manual page 1239

Chapter 60 Configuring Active/Active Failover
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Device Initialization and Configuration Synchronization
Configuration synchronization occurs when one or both units in a failover pair boot. The configurations
are synchronized as follows:
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When the replication starts, the adaptive security appliance console on the unit sending the configuration
displays the message "Beginning configuration replication: Sending to mate," and when it is complete,
the adaptive security appliance displays the message "End Configuration Replication to mate." During
replication, commands entered on the unit sending the configuration may not replicate properly to the
peer unit, and commands entered on the unit receiving the configuration may be overwritten by the
configuration being received. Avoid entering commands on either unit in the failover pair during the
configuration replication process. Depending upon the size of the configuration, replication can take
from a few seconds to several minutes.
On the unit receiving the configuration, the configuration exists only in running memory. To save the
Note
configuration to the flash memory on both units, select File > Save Running Configuration to flash
from the menu bar in the system execution space on the unit that has failover group 1 in the active state.
Startup configurations saved on external servers are accessible from either unit over the network and do
not need to be saved separately for each unit. Alternatively, you can copy the contexts configuration files
from the disk on the primary unit to an external server, and then copy them to disk on the secondary unit,
where they become available when the unit reloads.
Command Replication
After both units are running, commands are replicated from one unit to the other as follows:
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Note
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A failover occurs.
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You manually force a failover.
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You configured preemption for the failover group, which causes the failover group to
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automatically become active on the preferred unit when the unit becomes available.
When both units boot at the same time, each failover group becomes active on its preferred unit after
the configurations have been synchronized.
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 regardless of the primary or
secondary designation of the booting unit.
When both units boot simultaneously, the secondary unit obtains the running configuration from the
primary unit.
Changes 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.
Changes 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.
Information About Active/Active Failover
Cisco ASA 5500 Series Configuration Guide using ASDM
60-3