"Tactical" /24 announcements

Tom Hill tom at ninjabadger.net
Thu Aug 12 14:42:57 UTC 2021

On 11/08/2021 14:09, Jon Lewis wrote:
> What sort of hands-on experience is this opinion based on?

Having an upstream provider that did it, in a very aggressive fashion.

> I've done this manually in the past (quite some time ago), and done
> properly, it works fine.
> At least one major network hardware vendor has implemented it as a
> feature.  Turn it on, and the "deaggregates" with same next-hop as an
> aggregate are not programmed into the FIB.  The savings will vary
> depending on the device's connectivity, but I've seen >40%.

Limiting the pruning to cases with the same next-hop does indeed sound
like it would be safer than what I've seen done in the past.

Doing this with per-peer prefix-lists would not (certainly not in
classic IOS) provide you with the ability to compare the next-hop before
rejecting those more-specific prefixes, and likely why the attempts to
do this caused the problems that I'm referring to.

I'm glad to hear a vendor has implemented a useful knob. Which vendor?


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