FD value different from the 1st value in brackets

The following EIGRP topology table shows -
P 192.168.102.0/24, 1 successors, FD is 156160
via 192.168.11.1 (158720/128256), FastEthernet1/0
Why the FD is different from the FD value in brackets-158720?
Thanks in advance

topology.jpg

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Comments

smarkyo

i think this'll help with your 1st question...

https://supportforums.cisco.com/discussion/11382471/eigrp-equal-cost-metric-calculation-what-am-i-missing

i'm not 100% certain on your 2nd question, but the #1 thing about feasible successors is they need to be loop free.
if you judge only by the first value 158720, i don't think that's enough information to tell if that path is loop free.
using the 2nd value (the RD) will judge whether the path is loop free or not.

john_samson

Hi smarkyo ,but that link didnt answer to my questions

Jon_Cisco

The lines that you have given us don't really provide enough information to determine what is going on. I would expect the numbers to be the same if everything was set to defaults.

As for the Reported distance question. It has to do with knowing a path is loop free. A router can know many paths but it will only use loop free paths instantly.

You will want to look up the process of determining a loop free path and it should explain why the last hop is ignored in that calculation.

Good Luck.

john_samson

Giving free advices in forum doesn't mean you will give wrong info or post links .
ITS BETTER NOT TO ANSWER THAN POSTING LINKS OR GIVING HALF OR WRONG INFORMATION.

VinnyCisco

I would be careful trashing people. People are only trying to help you.

As far as telling someone their cert is useless, I do see you are CCENT certified, yet you can't answer a CCENT EIGRP Topic. Instead you ask others to do research for you and then lash out when you don't get what you want.

You wouldn't survive a day in IT with that attitude or temper, so maybe you should rethink your career path.

Have a good day, and good luck.

Dieg0M

It is very well explained in the link provided but in case it is not clear:
The FD is the lowest metric of the route since the last time the route went from Active to Passive state. The other number you see is the metric of the FD and will change in real time as you manipulate the other K values like bandwidth or delay. The "FD is " will not change untill the route goes from active to passive.

Jon_Cisco

john_samson wrote: »

Also,giving free advices in forum doesnt mean you will give wrong info or post links . That proves ur cert is useless and you havent gained any fruitful knowledge of networking!!!

ITS BETTER NOT TO ANSWER THAN POSTING LINKS OR GIVING HALF OR WRONG INFORMATION.

We are all here just trying to better our lives. This response really didn't need to be addressed but it was to funny so I had to.

Good Luck with your career. Keep asking questions but just realize were all just helping each other learn.

We do that by trying to answer questions we might not actually know the answer to. I actually learned something from this topic. I don't think it will come up on the ccna but you never know.

Here is a good link for your entertainment. Enjoy!

Let me google that for you

--chris--

Jon_Cisco wrote: »

We are all here just trying to better our lives. This response really didn't need to be addressed but it was to funny so I had to.

Good Luck with your career. Keep asking questions but just realize were all just helping each other learn.

We do that by trying to answer questions we might not actually know the answer to. I actually learned something from this topic. I don't think it will come up on the ccna but you never know.

Here is a good link for your entertainment. Enjoy!

Let me google that for you

You spelled the books name wrong

smarkyo

I read about EIGRP a couple weeks ago so I'm not an expert, but your post is something I've never seen in all of my 2 weeks

and left me intrigued enough to study it.

If you need a better answer, I think a board dealing with beyond CCNA would be the way to go because that feasible distance issue
is horrendously complex, but the way I'm understanding it...

The real definition of the feasible distance...
From Host X to Subnet Y, it's the the lowest metric in a period of time.
The period of time is reset each time a transition from Active to Passive occurs in the EIGRP topology table.
That transition occurs when DUAL algorithm is run (it'll go Passive to Active to Passive)

The DUAL algorithm runs when:
Something happens to your successor (it failed/cost modified) AND a Feasible Successor DOES NOT EXIST.
There is no feasible successor, so DUAL needs to run to find a replacement.
So the DUAL algorithm runs, the active to passive transition occurs, time period refreshes;
and you should see your Feasible Distance value updated & be matching in the topology table.

BUT...If a Feasible Successor DOES EXIST to replace the Successor.
DUAL does not need to run, there is no active to passive transition, time period DOES NOT refresh,
This is when you'll see mis-matched Feasible Distance Values because the previous FD value was "historically lowest"
and is still listed in the EIGRP topology table.

Also the "clear ip eigrp neighbors" will refresh the time period, so that should update FD values & they'll match.

john_samson

Hi I am sorry friends sometimes I get angry maybe out of frustration when I see you all posting links without explaining things in your own words. Please forgive me smarkyo.
And VinnyCisco , I passed my CCENT under old syllabus (640-822) which if you google can surely see that it didnt had EIGRP in ICND1.
Further I do apologize if I have hurt you all but I again stand my point - giving free advices doesn't mean that you will answer it by giving links to some other's posts which in itself isn't much informative or (in this case as I feel) doesnt relate to the query I posted except that the links discuss a similar but different issue related to EIGRP. But my eigrp prob is different from the prob in the link .
So I said that it is better to not to answer than giving incorrect or wrong information. Still anyways thanks for trying to answer. And I agree you sometimes not aware that you are not fully know about the problem you are answering . Good try though .

john_samson

Hi smarkyo
Are you really sure eigrp load-balancing is not covered in icnd2 or ccna?

Regards

john_samson

Hi smarkyo,
I asked 2 questions in my initial post, you or anyone else didnt even try to answer my 2nd question which is -
Why RD(Reported Distance also sometimes called as AD which is advertised distance) is used to compare with another AD to find the Feasible Successor(FS) and why not AD of some route is compared to AD of another route to find the FS?

Anyways I think this is beyond most people's knowledge so I leave it.

Better if there was some option I would have deleted this entire topic but alas no such options! So lets close this here
With Regards