[64075] in North American Network Operators' Group
Re: Pitfalls of annoucing /24s
daemon@ATHENA.MIT.EDU (Andy Ellifson)
Wed Oct 15 18:29:19 2003
Date: Wed, 15 Oct 2003 15:28:45 -0700 (PDT)
From: Andy Ellifson <andy@ellifson.com>
Reply-To: andy@ellifson.com
To: nanog@merit.edu
In-Reply-To: <751A658D-FF58-11D7-B14F-000A958F0F6A@isprime.com>
Errors-To: owner-nanog-outgoing@merit.edu
I have a /24 allocated to my by XO Communications in Phoenix, AZ
(67.X.X.0/24). I am currently announcing it to Verio in Europe. A
friend of mine that is an XO customer in Phoenix with BGP to XO can get
to that address block within XO's network.
But on the flip side. I also have a /22 from AT&T (12.X.X.0/22). When
I announce that network block to Verio in Europe (and nowhere else),
only certain places get to the Europe location. Networks that prefer
AT&T go to AT&T's network and die since the route isn't there. I don't
know if I am missing something but it think it may have to do with how
the network's peering/filter schemes work.
I may just be walking around the problem since I am a transit customer
of Verio and they normally filter.
-Andy
--- Phil Rosenthal <pr@isprime.com> wrote:
>
> On Oct 15, 2003, at 5:24 PM, H. Michael Smith, Jr. wrote:
>
> >
> >
> > What about the /24's that many ISPs (especially tier 2-3) are
> assigning
> > to multi-homed customers? What about an IX or "critical
> infrastructure
> > providers" that may be issued a /24 from ARIN (Policy 2001-3)?
> >
> As long as it's provider assigned, and your provider announces the
> supernet that the /24 is from, it will still work. If you announce
> PI
> space out of the old class A space in /24's, many networks wont be
> able
> to reach you.
>
