Network Router User Manual

Chapter 9: VRRP Configuration Guide
104 SmartSwitch Router User Reference Manual
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:
• As specified in RFC 2338, a Backup router that has transitioned to Master will not
respond to pings, accept telnet sessions, or field SNMP requests directed at the virtual
router's IP address.
Not responding allows network management to notice that the original Master router
(i.e., the IP address owner) is down.
ip-redundancy create vrrp 1 interface test-A
ip-redundancy create vrrp 1 interface test-B