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Dimension ES-4024 Ethernet Switch

VRRP 21-1

This chapter shows you how to configure and monitor the Virtual Routing Redundancy Protocol (VRRP)

on the ES.

21.1 VRRP Overview

Each host on a network is configured to send packets to a statically configured default gateway (the ES). The

default gateway can become a single point of failure. Virtual Routing Redundancy Protocol (VRRP), defined in

RFC 2338, allows you to create redundant backup gateways to ensure that the default gateway of a host is always

available.

In VRRP, a virtual router (VR) represents a number of physical layer-3 devices. An IP address is associated with

the virtual router. A layer-3 device having the same IP address is the preferred master router while the other Layer-

3 devices are the backup routers. The master router forwards traffic for the virtual router. When the master router

becomes unavailable, a backup router assumes the role of the master router until the master router comes back up

and takes over.

The following figure shows a VRRP network example with the ES A and B implementing one virtual router VR1 to

ensure the link between the host X and the uplink gateway G. Host X is configured to use VR1 (192.168.1.20) as

the default gateway. If the ES A has a higher priority, it is the master router. ES B, having a lower priority, is the

backup router.

Figure 21-1 VRRP: Example 1

If the ES A (the master router) is unavailable, the ES B takes over. Traffic is then processed by switch B.

Chapter 21

VRRP

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ZyXEL Communications Ethernet switch Guide de l'utilisateur Page 153