CCIE Practical Studies: Security (CCIE Self-Study)

Hot Standby Router Protocol Overview

Hot Standby Router Protocol (HSRP) can provide high network availability because it has the ability to route IP traffic for your hosts, whether it is on Ethernet, Fiber Distributed Data Interface (FDDI), or Token Ring networks, without relying on the availability of any single router. You use HSRP to group routers so that they can select an active router and a standby router. The active router is the router that is used to route packets; the standby router is a router that can take over the routing duties when an active router fails or when your predefined conditions are met.

HSRP is most useful when used with hosts that do not support a router discovery protocol, such as ICMP Router Discovery Protocol (IRDP), ...