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• Several virtual master routers configured for mutual backup and load sharing.
Load sharing can be accomplished by assigning a subset of addresses to different
host address pools using the DHCP server. (See "Configuring Address Pools" on
page 3-191.)
Router 1
VRID 23 (Master)
IP(R1) = 192.168.1.3
IP(VR23) = 192.168.1.3
VR Priority = 255
VRID 25 (Backup)
IP(R1) = 192.168.1.3
IP(VR25) = 192.168.1.5
VR Priority = 100
Virtual Router Redundancy Protocol
Virtual Router Redundancy Protocol (VRRP) allows you to configure a group of
routers as a single virtual router. The virtual router group is configured with a single
virtual IP address that can be used as the default gateway for host devices on the
attached network.
Configuring VRRP Groups
To configure VRRP, select an interface on one router in the group to serve as the
master virtual router. This physical interface is used as the virtual address for the
router group. Now set the same virtual address and a priority on the backup routers,
and configure an authentication string. You can also enable the preempt feature
which allows a router to take over as the master router when it comes on line.
Command Usage
Address Assignment –
• The IP address assigned to the virtual router must already be configured on the
router that will be the Owner. In other words, the IP address for the virtual router
exists on one, and only one, router in the virtual router group, and the network
mask for the virtual router address is derived from the Owner. The Owner will also
assume the role of the Master virtual router in the group.
• If you have multiple secondary addresses configured on the current VLAN
interface, you can add any of these addresses to the virtual router group.
• The interfaces of all routers participating in a virtual router group must be within the
same IP subnet.
LAN Segment A
Hosts (192.168.1.10-99)
Configuring Router Redundancy
Router 2
VRID 23 (Backup)
IP(R1) = 192.168.1.5
IP(VR23) = 192.168.1.3
VR Priority = 100
VRID 25 (Master)
IP(R1) = 192.168.1.5
IP(VR25) = 192.168.1.5
VR Priority = 255
LAN Segment B
Hosts (192.168.1.100-250)
3
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