Cisco ASA 5505 Configuration Manual page 1193

Information About High Availability
This chapter provides an overview of the failover features that enable you to achieve high availability on
the Cisco 5500 series adaptive security appliances. For information about configuring high availability,
see
Failover."
This chapter includes the following sections:
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Information About Failover and High Availability
Configuring high availability requires two identical adaptive security appliances connected to each other
through a dedicated failover link and, optionally, a Stateful Failover link. The health of the active
interfaces and units is monitored to determine if specific failover conditions are met. If those conditions
are met, failover occurs.
The adaptive security appliance supports two failover configurations, Active/Active failover and
Active/Standby failover. Each failover configuration has its own method for determining and performing
failover.
With Active/Active failover, both units can pass network traffic. This also lets you configure traffic
sharing on your network. Active/Active failover is available only on units running in multiple context
mode.
With Active/Standby failover, only one unit passes traffic while the other unit waits in a standby state.
Active/Standby failover is available on units running in either single or multiple context mode.
Both failover configurations support stateful or stateless (regular) failover.
OL-20339-01
Chapter 60, "Configuring Active/Active Failover"
Information About Failover and High Availability, page 57-1
Failover System Requirements, page 57-2
Failover and Stateful Failover Links, page 57-2
Active/Active and Active/Standby Failover, page 57-5
Stateless (Regular) and Stateful Failover, page 57-6
Auto Update Server Support in Failover Configurations, page 57-8
Failover Health Monitoring, page 57-10
Failover Feature/Platform Matrix, page 57-12
Failover Times by Platform, page 57-12
Failover Messages, page 57-13
C H A P T E R
or Chapter 59, "Configuring Active/Standby
Cisco ASA 5500 Series Configuration Guide using ASDM
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