Cisco Hot Standby Router Protocol (HSRP)

Status of this Memo This memo provides information for the Internet community. It does not specify an Internet standard of any kind. Distribution of this memo is unlimited. This document reflects an existing deployed protocol. The IETF does have a working group which is in the process of producing a standards track protocol to address the same issues. Abstract The memo specifies the Hot Standby Router Protocol (HSRP). The goal of the protocol is to allow hosts to appear to use a single router and to maintain connectivity even if the actual first hop router they are using fails. Multiple routers participate in this protocol and in concert create the illusion of a single virtual router. The protocol insures that one and only one of the routers is forwarding packets on behalf of the virtual router. End hosts forward their packets to the virtual router. The router forwarding packets is known as the active router. A standby router is selected to replace the active router should it fail. The protocol provides a mechanism for determining active and standby routers, using the IP addresses on the participating routers. If an active router fails a standby router can take over without a major interruption in the host's connectivity. This memo also discusses the ARP, MAC address, and security issues with this protocol.