[ipv6-wg] Re: Re: [address-policy-wg] Re: Andre's guide to fix IPv6

jeroen at unfix.org (Jeroen Massar) wrote:

> Elmar K. Bins wrote:
> How can you calling yourself a 'fat-fingered jerk' upset me ? :)

;-)

> > These filters do not exist to blind out small PI assignments, they are
> > in place to remove accidental leakage of IGP prefixes caused by some
> > fat-fingered jerk like myself...
> 
> So you filter on a /24 because of IGP, thus you will leak out a /23?

Wrong train of thought.

I am of course not leaking anything from my network (first, I train
my fingers every day, so they don't get fat, second, I do not redistribute
IGP prefixes). The /24 filters we are talking about here are filtering
other people's longer-than-/24s out.

The /24 filter is just a partly brain-damaged, partly geniously simple
way of removing a lot of fat-fingering from my routing table (I am not
one of the big transit ISPs, so I'm very happy with that).

> Adding 8 or so prefixes doesn't really get noticed by many people, but
> adding 10k does.

There are companies that run a /20 or bigger nicely sliced into small
networks (hundreds or thousands), and sometimes their IGP prefixes leak.


> Filtering based on routing-DB information is thus much
> better than doing it based on some arbitrary limit.

The effort of rebuilding an appropriate ACL every day, the length of the
ACL and the router processing degradation or - even worse - running into
hard limits, alongside the "update how often?" question prohibit that
largely. Of course, having an up-to-date ACL in sync with the routing
databases would be the ideal solution, or would it? How many people
don't register? How many DBs are there to track? Well...

But you have distracted me from the matter at hand, so I repeat again that
the /24 filters are not in place to filter out small PI blocks. It's not
nice, it's not perfect, but it's there. So any authority that gives out
networks (hello RIPE!) should consider everything longer than a /24 as
"non routable", and not give out such blocks as v4 PI.

Cheers,
	Elmi.