nanog mailing list archives

Re: /27 the new /24


From: Michael Still <stillwaxin () gmail com>
Date: Fri, 2 Oct 2015 13:08:16 -0400

There are lots of transits that will take le 32 on their customers inbound
but filter le 24 on egress announcements.

On Fri, Oct 2, 2015 at 12:47 PM, Jason Baugher <jason () thebaughers com>
wrote:

Are you suggesting that the Tier 1 and 2's that I connect to are not
filtering out anything shorter than /24? My expectation is that they are
dropping shorter than /24, just like I am.

Correct me if I'm wrong, but every *NOG BGP best practices document I've
read has advocated dropping all prefixes shorter than /24 at ingress and
egress.

On Fri, Oct 2, 2015 at 11:34 AM, William Herrin <bill () herrin us> wrote:

On Fri, Oct 2, 2015 at 11:55 AM, Suresh Ramasubramanian
<ops.lists () gmail com> wrote:
Besides which more than one provider filters by a minimum prefix length
per /8 - wasn't  Swisscom or someone similar doing that?  So multi
homing with even a /24 is somewhat patchy in terms of effectiveness

Hi Suresh,

That hasn't been true for something like a decade. Anybody who filters
anything shorter than /24 without also taking a default route (or the
equivalent) is not fully connected to the Internet.

Regards,
Bill Herrin



--
William Herrin ................ herrin () dirtside com  bill () herrin us
Owner, Dirtside Systems ......... Web: <http://www.dirtside.com/>





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