[Q] BGP filtering policies

Tue Apr 9 19:34:44 UTC 2002

If you'll look at this pointer to one of ARIN's pages, it lists
the minimum allocation size for each CIDR block that IANA has
given ARIN to manage.  From what I've seen, most providers accept
at least up to the prefix length that the RIR's are using, if not
longer.

http://www.arin.net/statistics/index.html#ipv4issued2002

Unfortunately, this doesn't help in your case.  My company also
has /14's from the traditional class A space.  I know of only one
case in two years where a customer reported a problem arising 
from holding a small assignment out of these blocks, which was 
ultimately corrected by renumbering the customer, a solution which
does not scale well.

Worst case, however, unless your UUNet connection goes down, you'll
still be able to reach most places via your other transit and peering
(since /24 is the closest thing to a "universal" allowed prefix length)
and will have full reachability via UUNet.  IMHO, accepting up to /24
in any of the space listed on the above URL is good service provider
practice.

> -----Original Message-----
> From: Henry Yen [mailto:henry at AegisInfoSys.com]
> Sent: Tuesday, April 09, 2002 2:11 PM
> To: nanog at merit.edu
> Subject: [Q] BGP filtering policies
> 
> 
> 
> We were recently assigned a /22 from UUNet in conjunction with some
> transit we're buying from them.  The space is inside their superblock,
> 65.242.0.0/14.  We are concerned that our route announcement of this
> block would be filtered out by some other providers, as it's not
> class C/swamp space (or even class B space for that matter).
> Verio's current policy, for one, indicates that this would be so.
> 
> This is of particular concern to us as our little network encompasses
> several physical partially-meshed locations, with a mix of varying
> bandwidths both upstream as well as intra-location.  Traffic 
> Engineering
> is what we think is a reasonable (business) approach to address our
> flexibility needs, and so we're trying to move to address 
> space(s) that
> would be least likely to be BGP filtered.
> 
> We've asked for a different block from UUNet but the request didn't
> meet with success; UUNet suggested that any problems encountered
> as a result of this allocation could probably solved by e-mailing
> any NSP whose traffic interchange with us might be negatively
> affected (unlikely, to be sure, but still...), and would then
> change their filter (I'm unconvinced of this scenario).
> 
> I briefly browsed the NANOG archives, and didn't see this 
> issue discussed
> recently.  Have the BGP filtering policies for "most" ISP/NSP's been
> relaxed to the level of "accept /24's from class A 
> (ARIN-allocated) space"?
> Am I mis-reading Verio's posted policy?  Is there anyone from UUNet
> who might choose to comment?  Is there something else I'm 
> misunderstanding?
> 
> -- 
> Henry Yen                                       Aegis 
> Information Systems, Inc.
> Senior Systems Programmer                       Hicksville, New York
> 