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Configuring the Switch
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Configuring Router Redundancy
Router redundancy protocols use a virtual IP address to support a primary router
and multiple backup routers. The backup routers can be configured to take over the
workload if the master router fails, or can also be configured to share the traffic load.
The primary goal of router redundancy is to allow a host device which has been
configured with a fixed gateway to maintain network connectivity in case the primary
gateway goes down.
This switch supports both the Virtual Router Redundancy Protocol (VRRP) and Hot
Standby Router Protocol (HSRP). These protocols are very similar. The primary
difference is that VRRP requires you to specify the interface of one of the routers
participating in the virtual group as the address for the master virtual router, while
HSRP requires you to configure an arbitrary address for the virtual master router.
Both protocols then select the backup routers based on the specified virtual router
priority. HSRP also includes the ability to dynamically modify the virtual router
priority based on the operational state of other interfaces on the router.
Router redundancy can be set up in any of the following configurations. The
following examples show configuration settings for VRRP. The only difference for
HSRP is that the virtual router IP address is never a real address, and the master
router is selected based on priority only.
• A master virtual router with one or more backup routers.
• Several virtual master routers using the same set of backup routers.
Master Router
Backup Router
Virtual Router (VR23)
VRIP = 192.168.1.3
VRID 23
IP(R1) = 192.168.1.3
IP(VR23) = 192.168.1.3
VR Priority = 255
VRID 23
IP(R2) = 192.168.1.5
VRIP(VR23) = 192.168.1.3
VR Priority = 100
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 Router
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