Is it normal if the VRRP preemption delay configured on an AR router is different from actual delay

Is it normal if the VRRP preemption delay configured on an AR router is different from actual delay?
It is normal. The backup-to-master conversion procedure for VRRP devices is as follows:
Backup device:
If the backup device receives packets with priority being 0 (lower than the priority of its own packets), the timer is set to Skew_time (offset time). If the packet priority is not 0, the packets are discarded and the backup device changes to the master state immediately.

Master device:
The master device sends VRRP advertisement packets regularly, and publicizes its configuration information (priority, for example) and working state in the VRRP group. Based on the VRRP packets, the backup device determines whether the master device works normally.
- If the master device drops its master state (for example, it quits the backup group), it sends an advertisement packet with priority set to 0, to enable the backup device to change to the master state quickly without waiting for the timer specified by Master_Down_Interval to expire. This switchover time is referred to as the skew time, and is calculated based on the formula: �?56 - Backup device priority)/256 (unit: second).
- If the master device encounters a network fault and cannot send an advertisement packet, the backup device will not know the status of the master device immediately and is notified of the fault until the timer specified by Master_Down_Interval expires. In this case, the backup device considers that the master device cannot work normally and switches over to the master state. The value of Master_Down_Interval is calculated based on the formula: 3 x Advertisement_Interval + Skew_time (unit: second).

Note:
In a performance-unstable network, network congestion may result in a backup device failure to receive packets from the master device within the time specified by Master_Down_Interval. In this case, the backup device will automatically switch over to the master state. If the packets from the master device arrive then, the device switches back to the backup state. This is likely to cause frequent switchover between VRRP devices. To relieve this phenomenon, a preemption delay can be configured to enable the backup device to wait for the preemption delay time after the timer specified by Master_Down_Interval expires. Before this relay time expires, the backup device will not switch over to the master state even if it does not receive an advertisement packet.

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