Hot Standby Router Protocol (HSRP) is a protocol developed by Cisco which provides high RFC , which are defined in Finding Feature Information; Information About FHRP – HSRP MIB; How to to RFC , which are defined in In computer networking, the Hot Standby Router Protocol (HSRP) is a Cisco proprietary redundancy protocol for establishing a fault-tolerant default gateway. Version 1 of the protocol was described in RFC in

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In this state the router is still waiting to hear from the active router.

It listens for Hello messages hsfp those routers. If the active router fails, the standby router takes over as the active router. If a router sends a Hello message, then receivers should consider that Hello message to be valid for one Holdtime. When comparing priorities of two different routers, the router with the numerically higher priority wins. This is the starting state and indicates that HSRP is not running.

Solved: hsrp and rfc – Cisco Community

Version 2 of the protocol introduces stability, scalability and diagnostic improvements. It contains the approximate period between the Hello messages that the router sends. A single router elected from the group is responsible for forwarding the packets that hosts send to the virtual router.

This router is known as the active router. To minimize network traffic, only the active and the standby routers send periodic HSRP messages once the protocol has completed the election process. This can be useful for dual branch routers each with a single link back to the gateway. In the event that the active router fails, the standby assumes the packet forwarding duties of the active router.

HSRP is not intended as a replacement for existing dynamic router discovery mechanisms and those protocols should be used instead whenever possible. If the virtual IP address is not configured on a router, then it MAY be learned from the Hello message from the active router.


Although an arbitrary number of routers may run HSRP, only the active router forwards the packets sent to the virtual router. This set is known as an HSRP group or a standby group.

HSRP gateways send multicast hello messages to other gateways to notify them of their priorities which gateway is preferred and current status active or standby. From Wikipedia, the free encyclopedia. By using this site, you agree to the Terms of Use and Privacy Policy. This page was last edited on 28 Decemberat For other media values between 0 and inclusive are valid.

A large class of legacy host implementations that do hsdp support dynamic discovery are capable of configuring a default router. For each standby group, a single well-known MAC address is allocated to the group, as well as an IP address.

Hot Standby Router Protocol

hrsp Cisco protocols First-hop redundancy protocols. If the link of the primary router goes down, the backup router will take over the primary functionality and thus retain connectivity to the gateway. Retrieved from rrfc https: If the primary router should fail, the router with the next-highest priority would take over hsep gateway IP address and answer ARP requests with the same MAC address, thus achieving transparent default gateway failover.

If the Hellotime is not configured on a router, then it MAY be learned from the Hello message from the active router. In particular, the protocol protects against the failure of the first hop router when the source host cannot learn the IP address of the first hop router dynamically.

It is not compatible with version 1 HSRP. The protocol is designed for use over multi-access, multicast or broadcast capable LANs e.


This field identifies the standby group. In the case of routers with equal priority the router with the higher IP address wins. If multiple groups are used on a single LAN, load splitting can be achieved by distributing hosts among different standby groups. It contains the amount of time that the current Hello message should be considered valid. If the standby router fails or becomes the active router, another router is elected as the standby router.

The router has not determined the virtual IP address, and not yet seen an authenticated Hello message from the active router. For Token Ring, values between 0 and 2 inclusive are valid. HSRP has the ability to trigger a failover if one or more interfaces on the router go down. There is no RFC for version 2 of the protocol. Views Read Edit View history.

If the Holdtime is not configured on a router, then it MAY be learned from the Hello message from the active router. This hwrp describes the current state of the router sending the message. Each standby group emulates a single virtual router. The router is a candidate to become the next active router and sends periodic Hello messages.

HSRP is not a routing protocol as it does not advertise IP routes or affect the routing table in any way. This state is entered via a configuration change or when an interface first comes up. On a particular LAN, multiple hot standby groups may coexist and overlap.