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294 CHAPTER 10: RELIABILITY
Perform the following configuration in VLAN interface view.
Configuring the Priority
of Switches
The status of each switch in the virtual router group is determined by its priority in
VRRP. The switch with the highest priority becomes the master.
The priority ranges from 0 to 255 (the greater the number, the higher the priority.
However only values from 1 to 254 can be used. Priority 0 is reserved for special
use and 255 is reserved for the IP address owner.
Perform the following configuration in VLAN interface view.
By default, the priority is 100.
The priority for an IP address owner is always 255, which cannot be changed.
Configuring Preemption
and Delay for a Switch
When a switch in the virtual router functions as a master switch, other switches,
even if they are configured with a higher priority later, cannot become the master
switch unless they are configured to work in preemption mode. The switch in
preemption mode can become the master switch when it finds that its own
priority is higher than the priority of the current master switch. If this happens, the
former master switch becomes the backup switch.
In addition to preemption settings, a delay can also be set. A backup switch waits
for a period of time before becoming a master. In an unstable network, if the
backup switch has not received packets from the master switch periodically, it
becomes the master switch. However, the failure of the backup switch to receive
packets may be due to network congestion instead of the malfunction of the
master switch. In this case, the backup switch receives the packets after a while.
The delay settings can thereby avoid a frequent change of status.
Perform the following configuration in VLAN interface view.
Table 3 Add/Delete a Virtual IP Address
Operation Command
Add a virtual IP address. vrrp vrid virtual-router-ID virtual-ip
virtual-address
Delete a virtual IP address. undo vrrp vrid virtual-router-ID [ virtual-ip
virtual-address ]
Table 4 Configure the Priority of Switches in the Virtual Router
Operation Command
Configure the priority of switches in the virtual
router.
vrrp vrid virtual-router-ID priority priority
Clear the priority of switches in the virtual
router.
undo vrrp vrid virtual-router-ID priority
Table 5 Configure Preemption and Delay for a Switch
Operation Command
Enable the preemption mode and configure a
period of delay.
vrrp vrid virtual-router-ID preempt-mode [
timer delay delay-value ]
Disable the preemption mode. undo vrrp vrid virtual-router-ID
preempt-mode