EIGRP auto-summarizes by default?

[MicJameson2]

I've received opposite data from AI GROK, and book CCNP Enterprise Advanced Routing and Switching, 2nd edition.

Grok says EIGRP auto-summarizes by default.

The CCNP book says opposite, as quiz answer "chapter 3, #6" on page 959.

Can someone please tell me the correct answer, and supply his data source?

Thank you.

[David Ruess · Accepted solution]

Hello,

I believe older versions of devices routing protocols used to auto-summarize. I believe newer devices do NOT auto-summarize by default.

I would refrain from using AI in your studies as these issues happen consistently enough to cause confusion in students. The study guides and the community here are very helpful when having these kinds of questions.

Hope this helps.

-David

[Joseph W. Doherty]

I believe David is correct, default behavior has changed over the years for this setting (which does happen).

[Elliot Dierksen]

Yes, I think @David Ruess is correct too. I just can't remember when that changed.

[Joseph W. Doherty]

Yea, very easy to miss when you've been changing the prior default to a new default, because end result is the same.

[Elliot Dierksen]

I can't answer it as it pertains to exam questions, but I always put in "no auto-summary" when using EIGRP. I think people frequently misunderstand what auto summary really means. If you have two networks, 10.1.1.0/24 and 172.31.5.0/24 that are in an EIGRP router and auto summary is on, here is what you will see. 10.0.0.0/8 will be advertised out the 172.31.5.0 network and 172.31.0.0/16 will be advertised out 10.1.1.0/24. When you cross classful boundaries like this, advertisements are summarized up to the class boundary.