Why auto-summary is enabled by default with EIGRP protocol?

[csco11502970]

Why auto-summary is enabled by default with EIGRP protocol?

[Jan Hrnko]

Hi Chetan,

I don't know if there is an answer to your question, but I just want to let you know that auto-summary is disabled by default on the newer IOSes (15). I am not 100 percent sure what changed their mind about that. Auto-summary has its pros and cons and maybe they think that nowadays it causes more harm than benefit. (As most of the time you want the auto-summarization to be turned off).

Best regards,

Jan

[Alessio Andreoli]

Hi there,
It is enabled because EIGRP is the evolution of a fully classful routing protocol (IGRP) where summarising classes had a different meaning than for us today summarising subnets..
Important issuing

Router EIGRP as_number
No auto

Each single time you configure EIGRP. It is very unlikely you are going to use the auto summary command in the modern networks.

Hope this helps
Alessio

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