Invalid Interval field:
Specifies the amount of time, in seconds, that, if no update has been received for a given route, the route is considered to have timed out. This value should be several times the update interval, in order to allow for the possibility that packets containing an update could be dropped by the network. This field displays only when the Use protocol defaults field is set to off.
Range: 1-65535
Default: 3 times the value in the Update Interval field.