Cisco® CCNA Exam Cram Notes : FHRP

VII. IP connectivity and Services


First Hop Redundancy Protocols (FHRP) are used to allow gateway redundancy. They are the redundancy protocol that allow a router on a LAN segment to automatically take over if another one fails. The purpose of a First Hop Redundancy Protocol (FHRP) is to provide IP Routing Redundancy by allowing transparent fail-over at the First-Hop IP Router.

Default gateway redundancy allows a network to recover from the failure of the device acting as the Default Gateway for end nodes on a physical segment. The ability of a network to dynamically recover from the failure of a device acting as a default gateway is known as First-Hop Redundancy.

The devices on this shared network segment are usually configured with a single default gateway address that points to the router that connects to the rest of the network. Layer 1 and Layer 2 redundancies, a high-availability network. It also implement layer 3 redundancy by sharing the default gateway responsibility across multiple devices.

  • Used in a group of routers for selecting an active device and a standby device.

  • A non-proprietary election protocol that allows several routers on a multi-access link to use the same virtual IPv4 address.

  • Cisco-proprietary FHRP protocol designed to allow for transparent failover of a first-hop IPv4 devices.

  • Cisco-proprietary FHRP protocol that protects data traffic from a failed router or circuit while also allowing load sharing between a group of redundant routers.

  • One router is elected as the virtual router master, with the other routers acting as backups in case the virtual router master fails.

There are three first hop redundancy protocols that could be used for this purpose:

HSRP,VRRP,GLBP. They provide alternate default gateways for hosts in the switched environment.

Hot Standby Router Protocol (HSRP): HSRP is a Cisco-Proprietary Redundancy Protocol for establishing a fault-tolerant default gateway. HSRP provides a transparent fail-over mechanism to the end stations on the network. This provides users at the access layer with uninterrupted service to the network if the primary gateway becomes inaccessible.

Virtual Router Redundancy Protocol (VRRP): VRRP is a standards-based alternative to HSRP. The two technologies are similar but not compatible.

Gateway Load Balancing Protocol (GLBP): Gateway Load Balancing Protocol (GLBP) is a Cisco proprietary solution for redundancy and load balancing in an IP network.

  • GLBP allow automatic selection and simultaneous recovery from first hop router failures.

  • GLBP provides load balancing over multiple (router) gateways using a single virtual IP address and multiple virtual MAC addresses.

  • Each host is configured with the same virtual IP address, and all routers in the virtual router group participate in forwarding packets.

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