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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The protocol is designed for use over multi-access, multicast or broadcast capable LANs hsfp. For Token Ring, values between 0 and 2 inclusive harp valid. A large class of legacy host implementations that do not support dynamic discovery are capable of configuring a default router. If the Hellotime is not configured on a router, then it MAY be learned from the Hello message from the active router. The virtual IP address used by this group. In the event that the active router fails, the standby assumes the packet forwarding duties of the active router.

Hot Standby Router Protocol

This field contains a clear text 8 character reused password. A single router elected from the group is responsible for forwarding the packets that hosts send to the virtual router. The router knows the virtual IP address, but is neither the active router nor the standby router. If the Holdtime is not configured on a router, then it MAY be learned from the Hello message from the active router.

For other media values between 0 and inclusive are valid. If the active router fails, the standby router takes over as the active router.

This field describes the current state of the router sending the message. If the link of the primary router goes down, the backup hsrrp will take over the primary functionality and thus retain connectivity to the gateway. The router sends periodic Hello messages. This set is known as an HSRP group or a standby group.


The router is currently forwarding packets that are sent to the group’s virtual MAC address. If the primary router should fail, the router with the next-highest priority would take rcf the gateway IP address and answer ARP requests with the same MAC address, thus achieving transparent default gateway failover.

Each standby group emulates a single virtual router. It contains the amount of time that the current Hello message should be considered valid.

HSRP, Hot Standby Router Protocol

It listens for Hello messages from those routers. In this state the router is still waiting to hear from the active router. When comparing priorities of two different routers, the router with the numerically higher priority wins.

Views Read Edit View history. It contains the approximate period between the Hello messages that the router sends.

In the case of routers with equal priority the router with the higher IP address wins. If the standby router fails or becomes the active router, another router is elected as the standby 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. On rcf particular LAN, multiple hot standby groups may coexist and overlap.

Solved: hsrp and rfc – Cisco Community

This is the starting state and indicates that HSRP is not running. HSRP is not a routing protocol as it does not advertise IP routes or affect the routing table in any way. A router cannot enter Speak state unless it has the herp IP address. For each standby group, a single well-known MAC address is allocated to the group, as well as an IP address. Retrieved from ” https: Another router is elected as the standby 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.

This page was last edited on 28 Decemberat From Wikipedia, the free encyclopedia. Version 2 of the protocol introduces stability, scalability and diagnostic improvements.

HSRP is not intended as a replacement for existing hsro router discovery mechanisms and those protocols should be used instead whenever possible. The protocol establishes an association between gateways in order to achieve default gateway failover if the primary gateway becomes inaccessible. If a router sends a Hello message, then receivers should consider that Hello message to be valid for one Holdtime.

By using this site, you agree to the Terms of Use and Privacy Policy. Cisco protocols First-hop hsp protocols. This can be useful for dual branch routers each with a single link back to the gateway. HSRP has the ability to trigger a failover if one or more interfaces on the router go down. HSRP provides failover services to those hosts. Although 2821 arbitrary number of routers may run HSRP, only the active router forwards the packets sent to the virtual router.