This read-write integer, from 1 to 2000 seconds, sets how long the interface waits after last hearing a neighbor's Hello packets before declaring that neighbor down, and this value is advertised in the router's own Hello packets. An administrator must set this consistently with all other routers on the same network to avoid premature or delayed neighbor-down declarations. For example, this dead interval is commonly set to several times the Hello interval so a few missed Hellos don't immediately trigger a false neighbor-down event.