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? -- Tom