In EIGRP does AD < FD or AD <=FD

[mirror512]

I am confused with Cisco EIGRP issue for feasible successor

Does AD < FD or AD <=FD

[SiThacHoang]

Now I am well aware of this question  from the Peter's reply and it is proven . Thanks so much !

[Peter Paluch]

Hello Hoang,

Thank you very much - thanks everyone for your kind words!

One correction, though: I was mistaken regarding the MTU usage in EIGRP. I am very thankful to Don Slice for his willingness to discuss this issue via private messages - and the result is that MTU metric factor is not used in any way in EIGRP path selection algorithm. Put simply, it is unused indeed.

I apologize for spreading misconceptions about the MTU usage in EIGRP. It was my sincere belief based on information from, among others, Ivan Pepelnjak's blog, that the MTU was used as a second tiebreaker. However, it is not the case and I was wrong.

The MTU usage in EIGRP is a neverending story but it should be put to rest once and for all - it was envisioned but never implemented, and in the current EIGRP code, it is not used. It is as plain as that.

Once again, I sincerely apologize to everyone whom I have led to believe that EIGRP somehow uses the MTU value. It does not.

Best regards,

Peter

[Iluvnetwork]

Is this information still valid in 2017? 

Always learning priceless lessons from you :) You are the best!!!

[Iluvnetwork]

My understanding is that MTU is unused in EIGRP Metric Calculation, but MTU is used in the Best-Path Selection. If there are two best paths, packets will be sent to the path with the higher MTU size because less fragmentation happens with the higher MTU. If am wrong, please please let me know :)