This value is the number of seconds a DVMRP neighbor can go without being heard from before the router removes it from its neighbor list on that interface. An admin adjusts this to control how quickly the router reacts to a downed or unresponsive DVMRP neighbor, trading faster failure detection against the risk of premature timeouts on a lossy link. For example, the default of 35 seconds means a neighbor that misses probes for over half a minute gets purged from the interface's neighbor table.