34

VRRP

This chapter shows you how to configure and monitor the Virtual Router Redundancy Protocol (VRRP) on the Switch.

34.1 VRRP Overview

Each host on a network is configured to send packets to a statically configured default gateway (this Switch). The default gateway can become a single point of failure. Virtual Router 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 switches (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 switch A has a higher priority, it is the master router. Switch B, having a lower priority, is the backup router.

Figure 152 VRRP: Example 1

172.21.1.1

172.21.1.10

172.21.1.10

 

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GS-4012F/4024 User’s Guide