nanog mailing list archives
Re: Upstreams blocking /24s? (was Re: How Not to Multihome)
From: Jon Lewis <jlewis () lewis org>
Date: Mon, 8 Oct 2007 21:19:22 -0400 (EDT)
On Mon, 8 Oct 2007, Justin M. Streiner wrote:
As far as allowing prefixes longer than a /24, that decision was made when the Internet was considerably smaller than it is now, and many networks adopted /24 as the cutoff point. If you make the cutoff point smaller, what is the new point... /26? /32?
Anything longer than /24 is unlikely to propogate far on the internet. You can all check your filters to see. I just checked mine, and neither Level3 nor Time Warner has tried to send me anything longer than /24 in recent history. If they did, it'd show up as hits on a distribute-list deny rule.
Rather than ISPs relaxing filters, you're likely to see them get more strict, filtering shorter prefixes, when routers start falling over in the next few months.
Many networks see customers multi-homing as pretty easy justification to provide them with a /24 of PA space, even if they're small enough that justifying a /24 while single-homed wouldn't work.
This is actually in the ARIN "rules". Multihoming is justification (regardless of utilization) for one of the multihomed network's providers to assign them a /24.
---------------------------------------------------------------------- Jon Lewis | I route Senior Network Engineer | therefore you are Atlantic Net | _________ http://www.lewis.org/~jlewis/pgp for PGP public key_________
Current thread:
- Re: How Not to Multihome, (continued)
- Re: How Not to Multihome Patrick W. Gilmore (Oct 09)
- Re: How Not to Multihome Valdis . Kletnieks (Oct 09)
- Re: How Not to Multihome Joe Provo (Oct 08)
- Re: How Not to Multihome Andy Davidson (Oct 09)
- Re: How Not to Multihome Leo Vegoda (Oct 09)
- Re: How Not to Multihome Andy Davidson (Oct 09)
- Re: How Not to Multihome Leo Vegoda (Oct 09)
- Re: How Not to Multihome Scott Weeks (Oct 08)
- Upstreams blocking /24s? (was Re: How Not to Multihome) David Conrad (Oct 08)
- Re: Upstreams blocking /24s? (was Re: How Not to Multihome) Steven M. Bellovin (Oct 08)
- Re: Upstreams blocking /24s? (was Re: How Not to Multihome) Justin M. Streiner (Oct 08)
- Re: Upstreams blocking /24s? (was Re: How Not to Multihome) Jon Lewis (Oct 08)
- Re: Upstreams blocking /24s? (was Re: How Not to Multihome) Justin M. Streiner (Oct 08)
- Re: Upstreams blocking /24s? (was Re: How Not to Multihome) David Conrad (Oct 08)
- Re: Upstreams blocking /24s? (was Re: How Not to Multihome) Patrick W. Gilmore (Oct 08)
- Re: Upstreams blocking /24s? (was Re: How Not to Multihome) Keegan . Holley (Oct 09)
- Easy and hard multihoming (was: Re: Upstreams blocking /24s) David Barak (Oct 10)
- Upstreams blocking /24s? (was Re: How Not to Multihome) David Conrad (Oct 08)