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 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.
Hot Standby Router Protocol
The protocol is designed for use over multi-access, multicast or broadcast capable LANs e. HSRP is not intended as a replacement for existing dynamic router discovery mechanisms and those protocols should be used instead whenever possible. A large class of legacy host implementations that do not support dynamic discovery are capable of configuring a default router.
HSRP provides failover services to those hosts. This 228 is known as harp HSRP group or a standby group. 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. Another router is elected as the standby router.
In the event that the active router fails, the standby assumes the packet forwarding duties of 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 frc. If the active router fails, the standby router takes over as the active router.
If the standby router fails nsrp becomes the active router, another router is elected as the standby router. On a particular LAN, multiple hot standby groups may coexist and overlap.
Each standby group emulates a single virtual router. For each standby group, a single well-known MAC address is allocated to the group, as well as rgc IP address. If multiple groups are used on a single LAN, load splitting can be achieved by distributing hosts among different standby groups.
Information on RFC » RFC Editor
This field describes the current hspr of the router sending the message. This field is only meaningful in Hello messages. It contains the approximate period between the Hello messages that the router sends.
The time is given in seconds. If the Hellotime is not configured on a router, then it MAY be learned from the Hello message from the active router. It contains the amount of time that the current Hello message should be considered valid.
If a router sends a Hello message, then receivers should consider that Hello message to be valid for one Holdtime. If ysrp Holdtime is not configured on a router, then it MAY be learned from the Hello message from the active router. A router hdrp 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. This field is used to elect the active and standby routers.
Hot Standby Router Protocol – Wikipedia
When comparing priorities of two different routers, the router with the numerically higher priority wins. In the case of routers with equal priority the router with the higher IP address wins. This field identifies the standby group. For Token Ring, values between 0 and 2 inclusive are valid.
For other media ysrp between 0 and inclusive are valid. This field contains a clear text 8 character reused password.
The virtual IP address used by this group. If the virtual IP address is not configured on a router, then it MAY be learned from the Hello message from the active router.
This is the starting state and indicates that HSRP is not running.
This state is entered via a configuration change or when an interface first comes up. The router has not determined the virtual IP address, and not yet seen an authenticated Hello message from the active router. In this state the router is still waiting to hear from the active router.
The router knows the virtual IP address, but is neither the active router nor the standby router.
It listens for Hello messages from those rfv. A router cannot enter Speak state unless it has the virtual IP address. The router is a candidate to become the next active router and sends periodic Hello messages. The router is currently forwarding packets that are sent to the group’s virtual MAC address. The router sends periodic Hello messages.