First Hop Redundancy Protocol

Limitations:

End devices are normally configured with a single def gateway IPv4 address

Router Redundancy

One way to prevent a single point of failure at the DG is to implement a virtual router.

• Multiple routers are configured to work together to present the illusion of a single router
• by sharing an IP addr and a MAC addr, two or more routers can act as a single virtual router
• the IPv4 addr of the virtual router is configured as the DG for the workstations on a specific IPv4 segment

A redundancy protocol provides a mechanism for determining what router should take the active role ad DG

• Also determines when the fwd role must be taken over by standby router

When the active router fails, the redundancy protocol transitions the standby router to the new active router

VRRP communicates using hello protocol

VRRP Adverts are sent at 1 sec intervals One is elected as Master whereas all other routers are backups

HSRP

The role of the active standby routers is determined by HSRP election process.