VRRP interval timers
Hello intervals
Hello messages are sent from the master VRRP device to the backup devices. The purpose of the hello messages is to determine that the master device is still online. If the backup devices stop receiving hello messages for a period of time, as defined by the dead (or master-down-interval) interval, the backup devices assume that the master device is offline. When the master device is offline, the backup device with the highest priority assumes the role of the master device.
Dead interval
The dead interval is defined as the period of time for which backup devices wait for a hello message from the master device before assuming that the master device is offline. An immediate switchover to the backup device with the highest priority is triggered after the dead interval expires and there is no hello message from the master device. If a value for the dead interval is not configured, the default value is calculated as three times the hello interval plus the skew time. Skew time is defined as (256 – priority)/256.
Backup hello message state and interval
By default, backup devices do not send hello messages to advertise themselves to the master device. Hello messages from backup devices can be activated, and the messages are sent at 60-second intervals, by default. The interval between the backup hello messages can be modified.