- A. a backup route, stored in the routing table
- B. a primary route, stored in the routing table
- C. a backup route, stored in the topology table
- D. a primary route, stored in the topology table
Feasible Successors –
A destination entry is moved from the topology table to the routing table when there is a feasible successor. All minimum cost paths to the destination form a set.
From this set, the neighbors that have an advertised metric less than the current routing table metric are considered feasible successors.
Feasible successors are viewed by a router as neighbors that are downstream with respect to the destination.
These neighbors and the associated metrics are placed in the forwarding table.
When a neighbor changes the metric it has been advertising or a topology change occurs in the network, the set of feasible successors may have to be re- evaluated. However, this is not categorized as a route recomputation. Feasible successor is a route whose Advertised Distance (AD) is less than the Feasible
Distance (FD) of the current best path. A feasible successor is a backup route, which is not stored in the routing table but, stored in the topology table.