HSRP(Hot Standby Router Protocol) is a Cisco proprietary First Hop Redundancy Protocol (FHRP). HSRP first hop redundancy mechanism provides alternative path as a proactive action for any failure on a device. In this lesson, we will learn the protocol and in the following lessons, we will also learn HSRP Configuration. You can also view related RFC here.
By the way, HSRP Group numbers is mention at the beginning of the confiugration after “standby” keyword. There can be multiple groups of HSRP on an interface.
Hot Standby Router Protocol works with HSRP Groups. For each group, there are different routers that has different roles. These roles are:
• Active Router
• Standby Router
• Listenning Routers
The Active Router is the router that the traffic flow go through this router. It is the router that actively take place in the traffic flow in normal case.
The Standby Router is the backup of Active Router. When th active router fails then this router become Active and the traffic go through this router.
Lastly the Listening Router is other routers that are participating in the HSRP group.
The main two roles of HSRP are Active and Standby. For these roles, routers does an election between them. In this election two parameters are important. The elections are done according to two parameters. These are:
• Priority Values
• Interface IP Addresses