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
|Published (Last):||2 November 2012|
|PDF File Size:||1.3 Mb|
|ePub File Size:||13.27 Mb|
|Price:||Free* [*Free Regsitration Required]|
A router cannot enter Speak state unless it has the virtual IP address. If the active router fails, the standby router takes over as the active router.
Retrieved from ” https: If multiple groups are used on a single LAN, load splitting can be achieved by distributing hosts among different standby groups. The time is given in seconds. HSRP provides failover services to those hosts. HSRP is not a routing protocol as it does not advertise IP routes or affect the routing table in any way.
The router is a candidate to become the next active router and sends periodic Hello messages. Version 2 of the protocol introduces stability, scalability and diagnostic improvements. This field contains a clear text 8 character reused password. This is the starting state and indicates that HSRP is not running.
Efc contains the approximate period between the Hello messages that the router sends. The virtual IP address used by this group. 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. It listens for Hello messages from those routers. The router is currently forwarding packets that are sent to the group’s virtual MAC address. It contains hzrp amount of time that the current Hello message should be considered valid.
Hot Standby Router Protocol
In the case of routers with equal priority the router with the higher IP address wins. 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. Views Read Edit View history. There is no RFC for version 2 of the 228. Each standby group emulates a single virtual router.
This router is known as the active router. For each standby group, a single well-known MAC address is allocated to the group, as well as an IP address. HSRP has the ability to trigger a failover if one or more interfaces on the router go down. It is not compatible with version 1 HSRP. A single router elected from the hsrl is responsible for forwarding the packets that hosts send to the virtual router.
A large class of legacy host implementations that do not support dynamic discovery are capable of configuring a default router. For Token Ring, values between 0 and 2 inclusive are valid.
From Wikipedia, the free encyclopedia. This field is only meaningful in Hello messages. In particular, dfc protocol protects against the failure of the first hop router when the source host cannot learn the Rff address of the first hop router dynamically.
If the standby router fails or becomes the active router, another router is elected as the standby router. This field identifies the standby group. Although an arbitrary number of routers may run HSRP, only the active router usrp the packets sent to the virtual router. If the Hellotime is not configured on a router, then it MAY be learned from the Hello message from the active router. If the link of the primary router goes down, the backup router will take over rffc primary functionality and thus retain connectivity to the gateway.
This can be useful for dual branch routers each with a single link back to the gateway. In rcf state the router is still waiting to hear from the active router. This page was last edited on 28 Decemberat To minimize network traffic, only the active and the standby routers send periodic HSRP messages rtc the protocol has completed the election process. On a particular LAN, multiple hot standby groups may coexist and overlap.
In the event that the 2821 router fails, the standby assumes the packet forwarding duties of 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.
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.
The router has not determined the virtual IP address, and not yet seen an authenticated Hello message from the active hsrl.
The protocol establishes an association between gateways in order to achieve default gateway failover if the primary gateway becomes inaccessible.
Hot Standby Router Protocol – Wikipedia
Cisco protocols First-hop redundancy protocols. Another router is elected as the standby router. Jsrp a router sends a Hello message, then receivers should consider that Hello message to be valid for one Holdtime.
The router knows the virtual IP address, but is neither the active router nor the standby router. When comparing priorities of two different routers, the router with the numerically higher priority wins.