Chapter 14. Router, Supervisor, and Power Redundancy

This chapter covers the following topics that you need to master for the CCNP BCMSN exam:

• Router Redundancy This section discusses three protocols that are available on Catalyst switches to provide redundant router or gateway addresses. The protocols include Hot Standby Routing Protocol (HSRP), Virtual Router Redundancy Protocol (VRRP), and Gateway Load Balancing Protocol (GLBP).

• Supervisor and Route Processor Redundancy This section covers the methods that can be used on some Catalyst switch platforms to operate an active-standby pair of hardware modules in one chassis. The redundancy modes include Route Processor Redundancy (RPR), RPR+, Stateful Switchover (SSO), and Non-Stop Forwarding (NSF).

• Power Supply Redundancy This section explains how two power supplies can be used in a Catalyst 4500R or 6500 chassis. Both power supplies can be active; you can configure whether one supply provides the total chassis load or whether both supplies share the total load.

A multilayer switch can provide routing functions for devices on a network, as described in Chapter 13, "Multilayer Switching." If that switch happens to fail, clients have no way of having their traffic forwarded; their gateway has gone away.

Other multilayer switches can be added into the network to provide redundancy in the form of redundant router or gateway addresses. This chapter describes the protocols that can be used for redundant router addresses, load balancing across multiple routers, and load balancing into a server farm.

This chapter also describes the features that support redundancy in hardware. Within a single multilayer switch chassis, two supervisor modules with integrated route processors can be used to provide hardware redundancy. If an entire supervisor module fails, the other module can pick up the pieces and continue operating the switch. The same is true for redundant power supplies within a single chassis.