Vrrp; C Ha Pte R 55 Vrrp; Vrrp Overview - ZyXEL Communications XS3800-28 User Manual

Chapter 55 VRRP
C 5 5
HA PTER

VRRP

This chapter shows you how to configure and monitor the Virtual Router Redundancy Protocol (VRRP) on
the Switch.
55.1 VRRP O ve rvie w
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 ( and ) implementing one
A B
virtual router to ensure the link between the host and the uplink gateway . Host is configured
VR1 X G X
to use (192.168.1.20) as the default gateway. If switch has a higher priority, it is the master router.
VR1 A
Switch , having a lower priority, is the backup router.
B
Example 1
Fig ure 398
If switch (the master router) is unavailable, switch takes over. Traffic is then processed by switch .
A B B
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