[nsp] Direction of manual summarization

[Streiner, Justin]

On Thu, 24 Jul 2003, Cheung, Rick wrote:

> 	Thanks to everyone who replied on the 5 9's Infrastructure question
> posted recently.
>
> 	I have a question on manual summarization. In practice, with EIGRP
> in a hub/spoke network, do we typically summarize addresses towards the
> core, or summarize it to the spokes? The intent is to limit the EIGRP
> queries from rippling to the edge routers, as we're trying to work around
> CSCdr91621 on our edge 4232 L3s.

In your case summarizing toward the spokes would be best.  The core
generally needs to know about every route in the routing table, with some
exceptions.  In a hub and spoke network, any route that a spoke router
doesn't know how to handle locally should generally be defaulted to a hub
router.  This is a pretty common configuration using either EIGRP or OSPF
for things like ISPs with lots of dialup POPs that converge into a central
hub site for aggregation.  It might work for IS-IS as well, but I've never
messed with it.

Also, summarizing toward the spokes reduces the resources (router CPU,
memory, bandwidth) necessary for that router to know how to move packets.

jms