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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For Token Ring, values between 0 and 2 inclusive are valid. Version 2 of the protocol introduces herp, scalability and diagnostic improvements. If the standby router fails or becomes the active router, another router is elected as the standby router.
A router cannot enter Speak state unless it has the virtual IP address. HSRP is not a routing protocol as it does not advertise IP hwrp or affect the routing table in any way.
If the virtual IP address is not configured on a router, then it MAY be learned from the Hello message from the active router. When comparing priorities of two different routers, the router with the numerically higher priority wins.
This field describes the current state of the router sending the message. For each standby group, a single well-known MAC address is allocated to the group, as well as an IP address.
In the case of routers with equal priority the router with the higher IP address wins. It listens for Hello messages from those routers. A router which is in active state MUST Hdrp learn new values for the Hellotime 2218 the Holdtime from other routers, although it may continue to use values which it learned rfx the previous active router. Views Read Edit View history. The protocol is designed for use over multi-access, multicast or broadcast capable LANs e. HSRP has the ability to trigger a failover if one or more interfaces on the router go down.
The router has not determined the virtual IP address, and not yet seen an authenticated Hello message from the active router. Harp router sends periodic Hello messages. It is not compatible with version 1 HSRP. The virtual IP address used by this group. This can be useful for dual branch routers each with a single link back to the gateway. If the active router fails, the standby router takes over as the active router. There is no RFC for version 2 of the protocol.
Another router is elected as the standby router. If multiple groups are used on a single LAN, load splitting can be achieved by distributing hosts among different standby groups. This field is used to elect the active and standby routers. HSRP is not intended as a replacement gsrp existing dynamic router discovery mechanisms and those protocols should be used instead whenever possible. From Wikipedia, the free encyclopedia.
Hot Standby Router Protocol
A single router elected from the group is responsible for forwarding the packets that hosts send 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.
This state is entered via a configuration change or when an interface first comes up. Each standby group emulates a single virtual router. The router knows the virtual IP address, but is neither the active router nor the standby router.
Cisco protocols First-hop redundancy protocols. This field identifies the standby group. This is the starting state and indicates that HSRP is not running. HSRP gateways send multicast hello messages to other gateways to hsfp them of their priorities which gateway is hsfp and current status active or standby. On a particular LAN, rfx hot standby groups may coexist and overlap. If the Hellotime is not configured on a router, then it MAY be learned from the Hello message from the active router.
In the event that the active router fails, the standby assumes the packet forwarding duties of the active router. HSRP provides failover services to those hosts. It contains the amount of time that the current Hello message should be considered valid. Retrieved from ” https: For other media values between 0 and inclusive are valid.
Hot Standby Router Protocol – Wikipedia
The protocol establishes an association between gateways in order to achieve default gateway failover if the primary gateway becomes inaccessible. It contains the approximate period between the Hello messages that the router sends. If a router sends a Hello message, then receivers should consider that Hello message to be valid for one Holdtime.
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. This page was last edited on 28 Decemberat This set is known as an HSRP group or a standby group.
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.
The router is currently forwarding packets that are sent to the group’s virtual MAC address. This router is known as the active router.