[ppml] alternative realities (was PIv6 for legacy holders (/wRSA + efficient use))

Scott Leibrand sleibrand at internap.com
Thu Aug 2 12:06:43 EDT 2007


Does Cogent have a route to your /24?  Do they announce a covering 
aggregate?  If so, then you will retain reachability even to networks 
who filter your /24, via Cogent's aggregate..


Steven E. Petty wrote:
>    I'm not certain your assumptions are valid.  I know my workplace is
> currently multihomed using a /24 assigned from cogent in the 38.  This
> filter would remove my routes.  Under current ARIN policies, our two
> dozen or so hosts don't qualify us for a direct assignment/allocation
> despite multi-homing.
>    Steve
> -----Original Message-----
> From: Scott Leibrand [mailto:sleibrand at internap.com] 
> Sent: Wednesday, August 01, 2007 8:08 PM
> To: Paul Vixie
> Cc: ppml at arin.net
> Subject: Re: [ppml] alternative realities (was PIv6 for legacy holders
> (/wRSA + efficient use))
> <snip>
> If someone can come up with a helpful policy, I'm all ears.  But yes, I
> do think this kind of thing will be self-correcting, for one simple
> reason: you don't have to know who's doing it to filter effectively.  
> All you need to know is what the minimum allocation size for each
> address range is.  (I know you know all this already, but I'm sure there
> are others who don't.)  A quick look at
> http://www.iana.org/assignments/ipv4-address-space and
> http://www.arin.net/reference/ip_blocks.html gives me a pretty good idea
> that I could filter, more or less safely, anything larger than /8 in the
> 0/8 to 56/8 range (with a couple exceptions, like down to /20 in 24/8),
> down to /16 in the 128/8 to 172/8 range, down to /20 in the 63/8 to 99/8
> range, etc.  If I were to implement such a policy, I'd first take a good
> hard look at my BGP table (rather than the cursory look I just did), but
> it's by no means necessary to identify the specific players doing the
> deaggregation in order to appropriately filter it.
> <snip>
> -Scott
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