EIGRP - Auto-Summary

Unanswered Question
Jun 14th, 2007


I noticed this in many examples along with a production box.

Why do people disable auto summary on the routers with EIGRP?

I have this problem too.
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Richard Burts Thu, 06/14/2007 - 07:11


There are several reasons why people would turn off auto summarization. In my experience probably the most common reason is that their networks have discontiguous subnets in which auto summarization would create problems. No auto summary in this situation allows EIGRP to advertise all subnets where auto summary would result in hiding some of the subnets.



chris.lepa Thu, 06/14/2007 - 07:33

With auto-summarization on, EIGRP summarizes routes to the classful boundary. This isn't good, as a lot of networks have discontiguous subnets.


s.arunkumar Thu, 06/14/2007 - 22:58

one more reason,

As eigrp summarizes automatically at classful boundaries,it creates an entry in routing table pointing towards Null0.

Hence in some scenarios,the taffic will match

this entry and a black hole can be resulted in the network........:)


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