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65-2
Cisco ASA 5500 Series Configuration Guide using ASDM
Chapter 65 Information About High Availability
Failover System Requirements
Note When the security appliance is configured for Active/Active Stateful Failover, you cannot enable IPsec
or SSL VPN. Therefore, these features are unavailable. VPN failover is available for Active/Standby
failover configurations only.
Failover System Requirements
This section describes the hardware, software, and license requirements for ASAs in a failover
configuration.
This section includes the following topics:
• Hardware Requirements, page 65-2
• Software Requirements, page 65-2
• License Requirements, page 65-2
Hardware Requirements
The two units in a failover configuration must be the same model, have the same number and types of
interfaces, the same SSMs installed (if any), and the same RAM installed.
If you are using units with different flash memory sizes in your failover configuration, make sure the
unit with the smaller flash memory has enough space to accommodate the software image files and the
configuration files. If it does not, configuration synchronization from the unit with the larger flash
memory to the unit with the smaller flash memory will fail.
Software Requirements
The two units in a failover configuration must be in the same operating modes (routed or transparent,
single or multiple context). They must have the same major (first number) and minor (second number)
software version. However, you can use different versions of the software during an upgrade process; for
example, you can upgrade one unit from Version 8.3(1) to Version 8.3(2) and have failover remain active.
We recommend upgrading both units to the same version to ensure long-term compatibility.
License Requirements
The two units in a failover configuration do not need to have identical licenses; the licenses combine to
make a failover cluster license. See the “Failover Licenses (8.3(1) and Later)” section on page 4-28 for
more information.