An important aspect of the VRRP redundancy scheme is VRRP device priority. Priority determines the role that each VRRP device
plays and what happens if the virtual primary device fails.
If a VRRP device owns the IP address of the virtual device and the IP address of the physical interface, this device will
function as a virtual primary device.
Priority also determines if a VRRP device functions as a virtual device backup and the order of ascendancy to becoming a
virtual primary device if the virtual primary device fails. You can configure the priority of each virtual device backup with
a value of 1 through 254 using the priority command (use the vrrp
address-family command to enter the VRRP configuration mode and access the priority option).
For example, if device A, the virtual primary device in a LAN topology, fails, an election process takes place to determine
if virtual device backups B or C should take over. If devices B and C are configured with the priorities of 101 and 100, respectively,
device B is elected to become virtual primary device because it has the higher priority. If devices B and C are both configured
with the priority of 100, the virtual device backup with the higher IP address is elected to become the virtual primary device.
By default, a preemptive scheme is enabled whereby a higher priority virtual device backup that becomes available takes over
from the virtual device backup that was elected to become virtual primary device. You can disable this preemptive scheme using
the no preempt command (use the vrrp
address-family command to enter the VRRP configuration mode, and enter the no preempt command). If preemption is disabled, the virtual device backup that is elected to become virtual primary device remains the
primary until the original virtual primary device recovers and becomes primary again.
Preemption of a lower priority primary device is enabled with an optional delay.