Hot Standby Router Protocol

One way to achieve near-100 percent network uptime is to use HSRP, which provides network redundancy for IP networks, and ensures that user traffic immediately and transparently recovers from first hop failures in network edge devices or access circuits.

When two or more routers share an IP address and a MAC (Layer 2) address, they can act as a single "virtual" router. The members of the virtual router group continually exchange status messages. This way, one router can assume the routing responsibility of another if one is out of commission for either planned or unplanned reasons. Hosts continue to forward IP packets to a consistent IP and MAC address, and the changeover of devices that do the routing is transparent.