| 13.1 |  | Understanding Failover |
| 13.1.1 |  | PIX Security Appliance failover overview |

| It is important that a failed firewall device will not impair network security. The failover function for the Cisco Secure PIX Firewall provides a safeguard in case a PIX Security Appliance fails. When one PIX Security Appliance fails, another immediately takes its place. In order for failover to work, both firewalls must have the same software version, activation key type, Flash memory, and RAM.

In order for the failover process to work properly, there must be two PIX Security Appliances. These devices are referred to as the primary PIX Security Appliance and the secondary PIX Security Appliance. The primary PIX Security Appliance functions as the active PIX Security Appliance, performing normal network functions. The secondary PIX Security Appliance functions as the standby PIX, ready to take control should the active PIX Security Appliance fail to perform. When the primary PIX Security Appliance fails, the secondary PIX becomes active and the primary PIX Security Appliance goes on standby.

A failover occurs when one of the following situations takes place:

- A power-off or a power-down condition occurs on the active PIX
- The active PIX Security Appliance is rebooted
- A link goes down on the active PIX Security Appliance for more than 30 seconds
- The failover active message occurs on the standby PIX Security Appliance
- Block memory exhaustion occurs for 15 consecutive seconds or more on the active PIX Security Appliance

Failover methods
The two failover connection methods are:

1. Serial cable failover
2. LAN-based failover

Both methods have the same purpose and work in a similar manner. The difference lies in the way the primary firewall is connected to the secondary firewall.

For serial cable failover, the primary PIX Security Appliance is directly connected to the secondary PIX Security Appliance by means of a special failover cable. One end of this cable is labeled ‘primary’, which plugs into the primary PIX Security Appliance. The other end is labeled ‘secondary’ and it plugs into the secondary PIX Security Appliance. For LAN-based failover, the two PIX Security Appliances are not directly attached. Instead, the primary and secondary PIX Security Appliances are connected over an Ethernet LAN. Both of these methods will be discussed in greater detail later in this module.