Stateful Failover - Cisco ACE-4710-K9 Administration Manual

Chapter 7 Configuring Redundant ACE Appliances

Stateful Failover

Note
Note
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The election of the active member within each FT group is based on a priority
scheme. The member configured with the higher priority is elected as the active
member. If a member with a higher priority is found after the other member
becomes active, the new member becomes active because it has a higher priority.
This behavior is known as preemption and is enabled by default. You can override
this default behavior by disabling preemption. To disable preemption, use the
preempt command. Entering this command causes the member with the higher
priority always to assert itself and become active. See the
Group" section.
The ACE replicates flows on the active FT group member to the standby group
member per connection for each context. The replicated flows contain all the
flow-state information necessary for the standby member to take over the flow if
the active member becomes unresponsive. If the active member becomes
unresponsive, the replicated flows on the standby member become active when
the standby member assumes mastership of the context. The active flows on the
former active member transition to a standby state to fully back up the active flows
on the new active member.
By default, connection replication is enabled in the ACE.
After a switchover occurs, the same connection information is available on the
new active member. Supported end-user applications do not need to reconnect to
maintain the same network session.
The ACE does not replicate SSL and other terminated (proxied) connections from
the active context to the standby context.
The state information passed to the standby appliance includes the following data:
Network Address Translation (NAT) table based on information synchronized
•
with the connection record
• All Transmission Control Protocol (TCP) and User Datagram Protocol (UDP)
connections not terminated by the ACE
Cisco 4700 Series Application Control Engine Appliance Administration Guide
Overview of Redundancy
"Configuring an FT
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