Smaller than a /24 for BGP?

Tue Jan 24 18:35:26 UTC 2023

Hi,

On Tue, 24 Jan 2023, at 6:19 PM, Justin Wilson (Lists) wrote:
> Have there been talks about the best practices to accept things smaller than a /24? I qm seeing more and more scenarios where folks need to participate in BGP but they do not need a full /24 of space. 

Yes, I think one of the reasons this was done was to stop routing table bloat by people advertising lots of small more specific routes.

I see your point though - with ipv4 becoming harder and more expensive to source, there is maybe a case for allowing people to advertise smaller blocks and you could also argue for less wastage where people are advertising /24s when they only need a small percentage of those IPs.

The problem now is, regardless of the merits or not of changing that , so many routers and so many places (knowledge/experience, guides, books, documents, best practices etc) that refer to and advise filtering out prefixes smaller than /24, advertising it just wouldn’t be effective if you are trying to advertise something and expecting it to be available to all networks.

Look at the take up of IPv6 or RPKI and how long they have been around, pushed, recommended etc. Trying to get people to adopt and implement these practices/changes is a long process.

Ian

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