Information about high availability, Introduction to failover and high availability, C h a p t e r – Cisco ASA 5505 User Manual

Page 1289

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C H A P T E R

61-1

Cisco ASA 5500 Series Configuration Guide using the CLI

61

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 ASAs. For information about configuring high availability, see

Chapter 63,

“Configuring Active/Active Failover”

or

Chapter 62, “Configuring Active/Standby Failover.”

This chapter includes the following sections:

Introduction to Failover and High Availability, page 61-1

Failover System Requirements, page 61-2

Failover and Stateful Failover Links, page 61-3

Active/Active and Active/Standby Failover, page 61-8

Stateless (Regular) and Stateful Failover, page 61-9

Transparent Firewall Mode Requirements, page 61-11

Auto Update Server Support in Failover Configurations, page 61-12

Failover Health Monitoring, page 61-14

Failover Times, page 61-16

Failover Messages, page 61-16

Introduction to Failover and High Availability

Configuring high availability requires two identical ASAs 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 ASA 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.

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