To determine the failure of the active components several methods can be implemented. The IOS firewall can use the HSRP, which can be tuned to fail over in less than 1 second.
However, if using a PIX Firewall, configure a simple native "cable" failover. A LAN failover is possible. Both methods achieve switching times below 15 seconds.
The failover cable is the only additional hardware required to support PIX failover. In PIX 6.2 and later, a failover can be achieved with or without a failover cable. The failover cable is a modified RS-232 serial link cable with a speed setting of 9600 baud. In PIX Software Release 5.2 (188.8.131.52), the speed was changed to 115.2K baud. If a switchover occurs, the units swap the IP address and MAC addresses they are using to replace each other's presence on the network. This action is invisible to the network.
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