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Router Redundancy Commands
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• VRRP advertisements are sent to the multicast address 224.0.0.8. Using a
multicast address reduces the amount of traffic that has to processed by
network devices that are not part of the designated VRRP group.
• If the master router stops sending advertisements, backup routers will bid to
become the master router based on priority. The dead interval before
attempting to take over as the master is three times the hello interval plus half
a second
Example
vrrp preempt
This command configures the router to take over as the master virtual router for a
VRRP group if it has a higher priority than the current acting master router. Use the
no form to disable preemption.
Syntax
vrrp group preempt [delay seconds]
no vrrp group preempt
• group - Identifies the VRRP group. (Range: 1-255)
• seconds - The time to wait before issuing a claim to become the master.
(Range: 0-120 seconds)
Default Setting
Preempt: Enabled
Delay: 0 seconds
Command Mode
Interface (VLAN)
Command Usage
• If preempt is enabled, and this backup router has a priority higher than the
current acting master, it will take over as the new master. However, note that
if the original master (i.e., the owner of the VRRP IP address) comes back on
line, it will always resume control as the master.
• The delay can give additional time to receive an advertisement message from
the current master before taking control. If the router attempting to become the
master has just come on line, this delay also gives it time to gather information
for its routing table before actually preempting the currently active router.
Example
Console(config-if)#vrrp 1 timers advertise 5
Console(config-if)#
Console(config-if)#vrrp 1 preempt delay 10
Console(config-if)#