In EIGRP, a feasible successor is a neighbor whose reported distance is less than the feasible distance.
As stated above if a path elected as a FS, its RD should be less than the FD. That's ok, but what if the Reported Distance is equal to feasible distance, in such a case can this path be a Feasible Successor?
For instance, assume that you have 5 path to the destination network with the following values;
Path 1: FD-40, RD-20
Path 2: FD-40, RD-20
Path 3: FD-20, RD-10
Path 4: FD:50, RD-30
Path 5: FD:30, RD-10
Path 3 is Successor, and Path 5 is Feasible Successor, if RD must be less (and not equal)than the FD.
However, Path 1 and 2 RD's are equal to Path 3's FD, which is 20. Are these paths will be elected Feasible Successor and will participate in load balancing?
(because if a path is not a feasible successor, the path is not used in load balancing)
Thanks in advance
If the RD is equal to the FD, then the route is rejected.
The reason is clear: if the RD is the same as the FD, then in all probability the neighbor is connected to the next hop in exactly the same way as you are. So who is to say who has the closer route and can therefore offer an alternative route to whom? You might end up offering an alternate route to each other, which would be a loop.