First Hop Redundancy Protocol

What is First Hop Redundancy Protocol?

The FHRP is designated to protect the default gateway on a subnetwork by allowing two or more routers to provide backup for that address.

For example, HSRP, VRRP, GLBP, and VARP.

HSRP (Hot Standby Routing Protocol)

HSRP allows more than one router to function as the default gateway, but only one router will be active (forwarding traffic) and others will be standby (not forwarding traffic).

Virtual IP address:

The Virtual IP address will be the default gateway’s IP address.

Preemption:

It allows HSRP to elect an Active router based on Priority which is by default 100.

If Preemption is disabled the HSRP will elect an active router based on the highest IP address.

Track:

It allows HSRP to track a particular link. If the link goes down the HSPR will reduce the priority value by a certain value configured by the admin.

Hello Time:

HSRP will send Hello packets every 3 sec to ensure that the active router is still functioning.

Holdtime:

If the standby router does not receive Hello packets for 10 seconds, it will become the active router and forward traffic.

HSRP version 1 uses 224.0.0.2 for communication.

HSRP version 2 uses 224.0.0.102 for communication.

VRRP (Virtual Router Redundancy Protocol)

VRRP allows Two routers to function as the default gateway, one router will be the Master and the other will be the Backup router.

Master:

The master router always forwards traffic…

Backup:

If the master is down, the Backup router will become the master and forwards traffic.

Preemption:

It allows HSRP to elect the master router based on Priority which is by default 100.

If Preemption is disabled the VRRP will elect the master router based on the highest IP address.

Preemption is enabled by default in VRRP.

Track:

It allows VRRP to track a particular link. If the link goes down the VRRP will reduce the priority value by a certain value configured by the admin.

VRRP routers use 224.0.0.18 for communication.

GLBP (Gateway Load Balancing Protocol)

GLBP allows four routers to function as a default gateway but only one router will be the AVG (Active Virtual Gateway) and others will be AVFs (Active Virtual Forwarder). In GLBP each AVF will have a separate virtual MAC address. Only the AVG will answer the ARP requests and all the routers (AVFs) in GLBP just forward traffic.