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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Cisco protocols First-hop redundancy protocols. In the case of routers with equal priority the router with the higher IP address wins.
If a router sends usrp Hello message, then receivers should consider that Hello message to be valid for one Holdtime.
This state is entered via a configuration change or when an interface first comes up. If the active router fails, the standby router takes over as the active router. There is no RFC for version 2 of the protocol.
The router is currently forwarding packets that are sent to the group’s virtual MAC address. This field contains a clear text 8 character reused password. The router is a candidate to become the next active router and sends periodic Hello messages.
To minimize network traffic, only the active and the standby routers send periodic HSRP messages once the protocol has completed the election process. For other media values between 0 and inclusive are valid.
It listens for Hello messages from those routers. The protocol is designed for use over multi-access, multicast or broadcast capable LANs e. The time is given in seconds. On a particular LAN, multiple hot standby groups may coexist and overlap. 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. A large class of legacy host implementations that do not support dynamic discovery are capable of configuring a default router.
This set is known as an HSRP group or a standby group. This page was last edited on 28 Decemberat The router has not determined the virtual IP address, and not yet seen an authenticated Hello message from the active router.
If the Hellotime is not configured on a router, then it MAY be learned from the Hello message from the active router. If multiple groups are used on a single LAN, load splitting can be achieved by distributing hosts among different standby groups. This field describes the current state of the router sending the message. This field identifies the standby group. The virtual IP address used by this group.
The router knows the virtual IP address, but is neither the active router nor the standby router. 22281 field is only meaningful in Hello messages. For each standby group, a single well-known MAC address is allocated to the group, as well as an IP address.
For Token Ring, values between 0 and 2 inclusive are valid. Another router is elected as the standby router. HSRP provides failover services to those hosts.
Hot Standby Router Protocol
HSRP has the ability to trigger a failover if one or more interfaces on the router go down. In particular, the protocol protects against the failure of the first hop router when the source host cannot 2281 the IP address of the first hop router dynamically.
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. If the virtual IP address is not configured on a router, then it MAY be learned from the Hello message from the active router. Retrieved from ” https: This is the starting state and indicates that HSRP is not running. The router sends periodic Hello messages.
This field is used to elect the active and standby routers. Views Read Edit View history. A router which is in active state MUST NOT learn new values for the Bsrp and the Holdtime from other routers, although it may continue to use values which it learned from the previous active router.
HSRP, Hot Standby Router Protocol
If the link of the primary 221 goes down, the backup router will take over the primary functionality and thus retain connectivity to the gateway. It is not compatible with version 1 HSRP. Each standby group emulates a single virtual router. HSRP is not intended as a replacement for existing dynamic router discovery mechanisms and those protocols should be used instead whenever possible.
Although an arbitrary number of routers may run HSRP, only the active router forwards the packets sent to the virtual router.