| 13.1 |  | Understanding Failover |
| 13.1.4 |  | Failover and stateful failover |

| As stated earlier in the module, failover enables the standby PIX Security Appliance to take over the duties of the active PIX Security Appliance when the active PIX Security Appliance fails. Two types of failover are stateful failover and non-stateful failover . They are described in detail below:

1. Non-stateful failover is when the standby PIX Security Appliance becomes active, all connections are lost and client applications must perform a new connection to restart communication through the PIX Security Appliance. The disconnection happens because the active PIX Security Appliance does not pass the stateful connection information to the standby PIX Security Appliance.
2. Stateful failover is when the standby PIX Security Appliance becomes active, the current connection information is available at the new active PIX Security Appliance. End-user applications are not required to do a reconnect to keep the same communication session. The connections remain because of the stateful failover feature, which passes per-connection stateful information to the standby PIX Security Appliance.

Stateful failover requires a 100-Mbps Ethernet interface to be used exclusively for passing state information between the two PIX Security Appliances . This interface can be any of the following:

- A Category 5 crossover cable that connects the primary PIX Security Appliance to the secondary PIX
- A 100BaseTX half-duplex hub using straight Category 5 cables
- A 100BaseTX full duplex on a dedicated switch or dedicated virtual LAN (VLAN) of a switch

The PIX Security Appliance does not support the use of either Token Ring or Fiber Distributed Data Interface (FDDI) for the stateful failover dedicated interface. Data is passed over the dedicated interface using IP protocol 105. No hosts or routers should be on this interface.

Depending on the failure, the PIX takes from 15 to 45 seconds to cause a switchover. Applications not handled by stateful failover will then require time to reconnect before the active unit becomes fully functional.