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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A large class of legacy host implementations that do not 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.

The time is given in seconds. The virtual IP address used by this group. A router cannot enter Speak state unless it has the virtual IP address.

Hot Standby Router Protocol

If a router sends a Hello message, then receivers should consider that Hello message to be valid for one Holdtime. If the Hellotime hsgp not configured on a router, then it MAY be learned from the Frc message from the active router. Cisco protocols First-hop redundancy protocols. This set is known as an HSRP group or a standby group. On a particular LAN, multiple hot standby groups may coexist and overlap.

HSRP provides failover services to those hosts. Retrieved from ” https: Version 2 of the protocol introduces stability, scalability and diagnostic improvements.

This is the starting state and indicates that HSRP is not running. This field is only meaningful in Hello messages. HSRP has the ability to trigger a failover if one or more interfaces on the router go down. When comparing priorities of two different routers, the router with the numerically higher priority wins.


This can be useful for dual branch routers each with a single link back to the gateway. This field identifies the standby group. The router has not determined the virtual IP address, and not yet seen an authenticated 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. By using this site, you agree to the Terms of Use and Privacy Policy. This field contains a clear text 8 character reused password. It listens for Hello messages from those routers.

In the event that the active router fails, the standby assumes the packet forwarding duties of the active router. HSRP is not a routing protocol as it does not advertise IP routes or affect the routing table in any way.

If multiple groups are used on hsro single LAN, load splitting can be achieved by distributing hosts among different standby groups. From Wikipedia, the free encyclopedia. If the primary router should fail, the router with the next-highest priority would take over the gateway IP address and answer ARP requests with the same MAC address, thus achieving transparent default gateway failover.

Views Read Edit View history. For Token Ring, values between rffc and 2 inclusive are valid. The protocol establishes an association between gateways in order to achieve default gateway failover if the primary gateway becomes inaccessible.

Solved: hsrp and rfc – Cisco Community

A router which is in active state MUST NOT learn new values for the Hellotime and the Holdtime from other routers, although it may continue to use values which it learned from the previous active router. If the active router fails, the standby router takes over as the active router. Although an arbitrary number of routers may run HSRP, only the active router forwards the packets sent to the virtual router.


To minimize network traffic, only the active and the standby routers send periodic HSRP messages once the protocol has completed the election process. In this state the router is still waiting to hear from the active router. Another router is elected as the standby router.

It contains the amount of time that the current Hello message should be considered valid. The router sends periodic Hello messages. This state is entered via a configuration change or when an interface first hsgp up. This page was last edited on 28 Decemberat There is no RFC for version 2 of the protocol.

It contains the approximate period between the Hello messages that the router sends. HSRP is not intended as a replacement for existing dynamic router discovery mechanisms and those protocols should be used instead whenever possible.

If the link of the primary router goes down, the backup router will take hsr; the primary functionality and thus retain connectivity to the gateway. For other media values between 0 and inclusive are valid.