Feasibility condition
The feasible distance is the best metric to reach the destination or the best metric that was known
when the route went active. This value is used in the feasibility condition check. If the reported
distance of the router (the metric after the slash) is less than the feasible distance, the feasibility
condition is met and that path is a feasible successor. After the software determines it has a
feasible successor, it does not need to send a query for that destination.