Smaller than a /24 for BGP?

Mike Hammett nanog at
Sun Feb 5 17:25:45 UTC 2023

I suspect the initial question was related to scarcity and not traffic engineering.

-----Mike HammettIntelligent Computing SolutionsMidwest Internet ExchangeThe Brothers WISP

----- Original Message -----
From: Michael Bolton <mbolton at>
To: Mike Hammett <nanog at>, Chris <chris at>
Cc: nanog at
Sent: Sat, 04 Feb 2023 19:50:07 -0600 (CST)
Subject: RE: Smaller than a /24 for BGP?

I’m late to the conversation, but I would have to agree with most. Below a /24 route advertisement shouldn’t happen.

I have a /24 that I would love to advertise as 2 /25’s, but the affects on everyone else is just too much. I take full routes from 4 providers, and I certainly don’t want to add over 100K. Carriers and enterprises have to pay a lot for our edge routers doing bgp and most don’t want to upgrade. We would benefit from advertising /25’s but it hurt’s more than it helps.

I’m in the alarm industry and they still haven’t started adopting IPv6. If we allow /25 subnets, some industries will never change. In a sense, we have to “force” them to change.


From: NANOG < at> On Behalf Of Mike Hammett
Sent: Thursday, January 26, 2023 8:52 AM
To: Chris <chris at>
Cc: nanog at
Subject: Re: Smaller than a /24 for BGP?

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Implementing v6 is important, but unrelated to allowing smaller v4 prefixes.

Not taking a position either way if smaller v4 prefixes is good or bad.

Mike Hammett
Intelligent Computing Solutions<>
Midwest Internet Exchange<>
The Brothers WISP<>
From: "Chris" <chris at<mailto:chris at>>
To: "Justin Wilson (Lists)" <lists at<mailto:lists at>>
Cc: nanog at<mailto:nanog at>
Sent: Wednesday, January 25, 2023 2:24:29 PM
Subject: Re: Smaller than a /24 for BGP?
I would suggest that this is trying to solve the wrong problem.  To me this is pressure to migrate to v6, not alter routing rules.

Kind Regards,
Chris Haun

On Tue, Jan 24, 2023 at 12:21 PM Justin Wilson (Lists) <lists at<mailto:lists at>> 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.  Seems wasteful.  I know this would bloat the routing table immensely.  I know of several folks who could split their /24 into /25s across a few regions and still have plenty of IP space.

Justin Wilson
j2sw at<mailto:j2sw at>

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