[99924] in North American Network Operators' Group
Re: Upstreams blocking /24s? (was Re: How Not to Multihome)
daemon@ATHENA.MIT.EDU (Vince)
Tue Oct 9 07:26:29 2007
Date: Tue, 09 Oct 2007 12:25:30 +0100
From: Vince <jhary@unsane.co.uk>
To: surfer@mauigateway.com
CC: nanog@merit.edu
In-Reply-To: <20071008175244.6370CBFB@resin18.mta.everyone.net>
Errors-To: owner-nanog@merit.edu
Scott Weeks wrote:
>
>
> --- drc@virtualized.org wrote:
> On Oct 8, 2007, at 2:48 PM, Scott Weeks wrote:
>
>> However, if it's less than a /24 it won't get very far as most
>> upstreams block prefixes longer than a /24.
>
> I'm curious: a couple of people have indicated they do not believe
> this to be the case. Anybody have any hard data on what filters are
> actually in use today?
> --------------------------------------------
>
>
> I found two current policies. Other companies made it too hard to find...
>
>
> Sprint:
> # Customers may announce routes as small as /26 for ARIN IP address blocks obtained through Sprint. Customers may announce routes as small as /28 for RIPE and APNIC address blocks obtained through Sprint.
>
> # Peer block announcements and customer announcements for blocks obtained from other providers are limited to a /24 or smaller mask (/23, /22 etc.).
>
>
>
> AT&T:
> * not accept Customer route announcements smaller than a /24 network
>
>
Level3:
From the output of
whois -h rr.level3.net AS3356
<snip>
remarks: The following import actions are common to every
remarks: Level 3 non-customer peering session:
remarks:
remarks: - RFC1918 and other reserved networks and subnets are
remarks: not permitted.
remarks:
remarks: - Advertisements with reserved ASes in the path
remarks: (ie 64512 - 65535) are not permitted.
remarks:
remarks: - Prefixes shorter than /8 or longer than /24 are
remarks: not permitted.
<snip>
(the rest is useful reading too if you deal with level3 much)
Vince
> scott
