# EIGRP Feasible Successor Help

Member Posts: 23 ■□□□□□□□□□
I just can't believe I can't grasp this concept. Every time I think I have it correct I get the wrong answer. In the pic attached is a simple little network. The only K value being used in the calculation is the Delay metric.

Basically which route is going to become the Successor Route and will the other route become the Feasible Successor Route?

This is what I keep doing:
R1 -(5)- R2 -(10)- R3 -(10)- R5 -(5)- LAN = FD:30 AD:5
R1 -(5)- R4 -(10)- R5 -(5)- LAN = FD: 20 AD:5

When I do that math above I would say the route from R1-R4-R5 is the Successor Route. The other route since its AD is lower than the FD on the Successor Route would become the Feasible Successor. However that is wrong. What am I calculating wrong? I am not worried about bandwidth, just the delay.

Ken~

• Member Posts: 1,614 ■■■■□□□□□□
We then compare that to R1's FD which is 20.

25 < 20

So the route through R2 will not be considered a FS. This is a pain in the butt when you first start learning about so just keep practicing and it will become really easy before you know it
• Member Posts: 23 ■□□□□□□□□□
Hey FloOz, At first I didn't get what you were saying as the numbers didn't make sense. For some reason it just now clicked after reading EIGRP from the FLG book. The AD is from the next routers perspective, and that's how you got that number.

Thanks,

Ken~
• Member Posts: 1,614 ■■■■□□□□□□
Yeah sorry I didn't make that clearer. The AD is of the next hop router.