[j-nsp] Summarize Global Table

[Stefan Fouant]

You can use aggregate
/generated routes which require more specific contributing routes to become active, and then only advertise the protocol aggregate routes to your downstream nodes that have smaller tables, however you still need to create the aggregates which is a manual process.

You can get pretty creative however, in your definition of aggregates, so that they can encompass a large number of specifics - for example, if your downstream node only supported a FIB of a few routes, you could create 2 aggregates on the upstream node, perhaps 0/1 and 128/1.  This is an extreme example, but you get the idea.

As far as I know, there are no ways to automatically summarize along the lines of what you are getting at because routers aren't intelligent enough to determine what prefix masks to use for summarization without user input.

What you would need to accomplish what you are describing is some way to tell the device that you want to summarize all the routing information into x number of prefixes, and then have the router automatically compute the best summaries where routing information overlaps and can be consolidated into a single prefix/mask combination.

Stefan Fouant
JNCIE-SEC, JNCIE-SP, JNCIE-ER, JNCI
Technical Trainer, Juniper Networks

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Sent from my iPad

On Oct 25, 2011, at 12:21 PM, Brad Fleming <bdflemin at gmail.com> wrote:

> Are there any tricks to auto-summarize the contents of a RIB where the tributary routes are not originated locally?
> 
> Example:
> Input routes:
> prefix: 1.0.0.0/16, next-hop: 5.5.5.5
> prefix: 1.0.1.0/16, next-hop: 5.5.5.5
> prefix: 1.0.2.0/16, next-hop: 4.4.4.4
> prefix: 1.0.3.0/16, next-hop: 5.5.5.5
> 
> Consolidated, Installed routes:
> prefix: 1.0.0.0/14, next-hop: 5.5.5.5
> prefix: 1.0.2.0/16, next-hop: 4.4.4.4
> 
> Basically a way to consolidate total number of prefixes entering the FIB.
> 
> If such a thing existed we could feed non-Juniper, TCAM-based routers a smaller table but still maintain the advantages of best path, hot potato routing.
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