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VRRP Configuration Notes
•
The Master router sends keep-alive advertisements. The frequency of these keep-alive
advertisements is determined by setting the Advertisement interval parameter. The
default value is 1 second.
•
If a Backup router doesn't receive a keep-alive advertisement from the current Master
within a certain period of time, it will transition to the Master state and start sending
advertisements itself. The amount of time that a Backup router will wait before it
becomes the new Master is based on the following equation:
Master-down-interval = (3 * advertisement-interval) + skew-time
The skew-time depends on the Backup router's configured priority:
Skew-time = ( (256 - Priority) / 256 )
Therefore, the higher the priority, the faster a Backup router will detect that the Master
is down. For example:
–
Default advertisement-interval = 1 second
–
Default Backup router priority = 100
–
Master-down-interval = time it takes a Backup to detect the Master is down
= (3 * adv-interval) + skew-time
= (3 * 1 second) + ((256 - 100) / 256)
= 3.6 seconds
•
If a Master router is manually rebooted, or if its interface is manually brought down, it
will send a special keep-alive advertisement that lets the Backup routers know that a
new Master is needed immediately.
•
A virtual router will respond to ARP requests with a virtual MAC address. This virtual
MAC depends on the virtual router ID:
virtual MAC address = 00005E:0001XX
where XX is the virtual router ID
This virtual MAC address is also used as the source MAC address of the keep-alive
Advertisements transmitted by the Master router.
•
If multiple virtual routers are created on a single interface, the virtual routers must
have unique identifiers. If virtual routers are created on different interfaces, you can
reuse virtual router IDs.
For example, the following configuration is valid:
ip-redundancy create vrrp 1 interface test-A
ip-redundancy create vrrp 1 interface test-B
Internet Appliance User Reference Manual
Chapter 5: VRRP Configuration Guide
75
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