OSPF route summarization

[petercinvest]

what's the difference between OSPF route summarization and EIGRP route summarization?

[Joseph W. Doherty]

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Posting

Well they both summarize routes, how they differ is how summarization is supported on them.  For example, you can summarize routes on an ABR as they are sent into area zero.  EIGRP, I understand, can summerize on any router.

[Joseph W. Doherty]

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The Author of this posting offers the information contained within this posting without consideration and with the reader's understanding that there's no implied or expressed suitability or fitness for any purpose. Information provided is for informational purposes only and should not be construed as rendering professional advice of any kind. Usage of this posting's information is solely at reader's own risk.

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In no event shall Author be liable for any damages wha2tsoever (including, without limitation, damages for loss of use, data or profit) arising out of the use or inability to use the posting's information even if Author has been advised of the possibility of such damage.

Posting

Oh, just thought to add, for either, you need a topology and network addressing that lends itself to be summarized.  For OSPF that might be a little easier, as, for example, an OSPF area might be working out of a single address block, and by their nature, OSPF areas are a hiearchy off area zero.  For EIGRP, to take full advantage of how it can summarize, you'll need to give more thought to how you allocate your addresses across the physical topology.

[Jon Marshall]

Just to add to Joe's post.

Quite a bit really.

EIGRP can summarise anywhere within the EIGRP domain using the "ip summary-address eigrp .." interface command so it is very flexible in that regard and is one of it's major advantages as far as I am concerned.

OSPF can summarise between areas and when you redistribute external routes into the OSPF domain.

But what OSPF can't do is summarise within an area because every router within an area must have an identical LSA database.

If you plan your areas well then there should be no need to summarise but requirements change and we have seen a number of posts on these forums where people have wanted to summarise within an OSPF area and it just can't be done.

Not saying EIGRP is better than OSPF but for summarisation it is definitely more flexible.

Jon