Chapter 18: Configuring Router Redundancy
Router redundancy protocols use a virtual IP address to support a primary route r
and multiple backup routers. The backup routers can be config ured to ta ke over the
workload if the master router fails, or can also be configured to share the traffic load.
The primary goal of router redundan cy is to allo w a host device whi ch has been
configured with a fixed gateway to maintain network connect ivity in ca se th e pri mary
gateway goes down.
This switch supports the Virtual Router Redundancy Protocol (VRRP). VRRP allows
you to specify the interface of one of the routers participating in the virtual group as
the address for the master virtual router, or to configure an arbitrary address for the
virtual master router. VRRP then selects the backup routers based on the spe cified
virtual router priority.
Router redundancy can be set up in any of the following configurations. These
examples use the address of one of the participating routers as the master ro uter.
When the virtual router IP address is not a r eal ad dress, the ma ster ro uter is
selected based on priority. When the priority is the same on several competin g
routers, then the router with the highest IP address is selected a s the maste r.
• A master virtual router with one or more backup routers.
Virtual Router (VR23)
VRIP = 192.168.1.3

Master Router

VRID 23
IP(R1) = 192.168.1.3
IP(VR23) = 192.168.1.3
VR Priority = 255

Backup Router

VRID 23
IP(R2) = 192.168.1.5
VRIP(VR23) = 192.168.1.3
VR Priority = 100
• Several virtual master routers using the same set of backup routers.
Master Router
VRID 23
IP(R1) = 192.168.1.3
IP(VR23) = 192.168.1.3
VR Priority = 255
Master Router
VRID 25
IP(R2) = 192.168.2.17
IP(VR25) = 192.168.2.17
VR Priority = 255
Backup Route
r
VRID 23
IP(R3) = 192.168.1.4
IP(VR23) = 192.168.1.3
VR Priority = 100
VRID 25
IP(R3) = 192.168.2.18
IP(VR23) = 192.168.2.17
VR Priority = 100

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