A network with High Availability provides alternate means by which all
infrastructure paths and key servers can be accessed at all times. The Hot
Standby Routing Protocol is one of those software features configured to
provide Layer 3 redundancy to network hosts. HSRP optimization provides
immediate or link specific failover as well as a recovery mechanism. Virtual
Router Redundancy Protocol and Gateway Load Balancing Protocol are derivatives
of HSRP providing additional Layer 3 redundancy features such as load
balancing. High Availability is also accomplished by implementing a combination
of device, link or hardware component redundancy at strategic points in the
network. Optimal fault tolerance is provided by redundant Supervisor Engines in
Multi Layer switches that also host a variety of failover services in software.
Another Cisco High Availability feature is Single Router Mode which allows
failover to a second MSFC.