Smaller than a /24 for BGP?

Jon Lewis jlewis at
Tue Jan 24 19:04:12 UTC 2023

On Tue, 24 Jan 2023, William Herrin wrote:

> On Tue, Jan 24, 2023 at 10:19 AM Justin Wilson (Lists) <lists at> wrote:
>> Have there been talks about the best practices to accept things smaller than a /24?
> Hi Justin,
> The short version is: it could happen but it won't. There's no
> technical obstacle. It's purely administrative. Tens of thousands of
> organizations would have to agree to accept smaller prefixes.That
> would only happen if there was something in it for them to start doing
> so, something major. And even then it would be a hard lift. There
> isn't. Some of those organizations run BGP set up by the last guy, the
> current gut doesn't really grok it, and he certainly doesn't subscribe
> to any information channels where it's discussed. So it's not going to
> happen.

The "other problem" is, every day more gear receiving full routes gets 
closer to (or farther past) the point where the resources to hold either 
the FIB or RIB just aren't there.  For those using these devices, lowering 
the bar and bringing in another 100k or so routes in short order just 
isn't an option.  /24 has been the de facto threshold for routes in the v4 
table long enough that I wouldn't want to be dependent on that changing.

  Jon Lewis, MCP :)           |  I route
  StackPath, Sr. Neteng       |  therefore you are
_________ for PGP public key_________

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