This is the configured interval, in centiseconds, at which the current master sends VRRP advertisements to the group - backup routers don't send advertisements at all, only listen for them - and it's the value backup routers use to calculate how long to wait before assuming the master has failed. Shortening this interval makes failover detection faster after a real master failure, at the cost of more control-plane traffic and CPU overhead from more frequent advertisements. A value of 100 (1 second) is the common VRRPv2 default, while some deployments tighten this toward 30-50 centiseconds specifically to shave failover detection time for latency-sensitive services relying on the virtual gateway.