Comments on: EIGRP Feasibility Condition

By: Study4Pass

Study4Pass — Mon, 05 Oct 2026 01:56:31 +0000

This finally made the Feasibility Condition click for me. I kept mixing up Reported Distance and Feasible Distance, and the rule that a neighbor’s reported cost must be strictly less than my own best FD to become a feasible successor is such a clean way to pick out loop-free backup paths.
The split horizon section was an eye-opener too — I didn’t realize split horizon could keep a route from even being advertised in the first place, before the feasibility check ever runs. Working through the metric math on each router made it stick. Thanks for the hands-on lab approach.

By: Nathan

Nathan — Thu, 03 Sep 2026 13:33:22 +0000

In reply to Attila. Yes, your "other reason" is the trade-off discussed earlier in the article, and the situation we saw where R1 does not install a feasible successor (for destination 9.9.9.0) through R2, even though that's an alternative, but still loop-free path. By guaranteeing loop-free paths, we may also end up excluding some as well.

By: Attila

Attila — Sat, 15 Feb 2025 17:22:43 +0000

Hello.

So then there can be two reasons why RouterB’s Reported Distance (RD) to RouterA is bigger than RouterA’s Feasible Distance (FD).

One possible reason is that RouterA’s metric is included in RouterB’s FD calculation. That means that RouterA is part of a routing loop.

The other reason is that the cost between two or more routers is so high, that increases RouterB’s RD so much that it becomes bigger than RouterA’s FD. In that case, there’s no loop.

Is that correct?

By: asd

asd — Tue, 26 Nov 2024 08:00:04 +0000

In reply to Staso. It's not, you're getting confused here

By: Staso

Staso — Fri, 28 Jul 2023 14:31:15 +0000

it should be ” better than a path R2..” in the split horizon section

By: Ed Harmoush

Ed Harmoush — Tue, 29 Mar 2022 17:10:50 +0000

In reply to Cam.

Glad this helped, Cam =). All of my CCNA content is posted here: https://www.practicalnetworking.net/index/ccna/

By: Cam

Cam — Thu, 10 Feb 2022 02:16:03 +0000

Great article! Just came from some Cisco training and this seemed to explain this a bit more clearly.

By: Ed Harmoush

Ed Harmoush — Thu, 20 Jan 2022 23:40:48 +0000

In reply to Thilagaraj R. You're welcome!

By: Thilagaraj R

Thilagaraj R — Fri, 14 Jan 2022 14:57:56 +0000

Thank-you

By: Lucas

Lucas — Sun, 30 Sep 2018 09:51:29 +0000

One of the best article I have seen yet, that’s really going to help me pass the ICND2 and finally get the CCNA R&S!