filtering /48 is going to be necessary

Sascha Lenz slz at
Sat Mar 10 03:41:04 CST 2012

Hi all,

> Hi,
>> What should happen is this  "quasi-legitimate"  method  of
>> multi-homing should just be declared illegitimate for IPv6, to
>> facilitate stricter filtering. Instead, what should happen is the
>> multi-homing should be required to fit into one of 3 scenarios,  so
>> any announcement with an IPv6 prefix length other than the
>> RIR-allocated/assigned PA or PI block size can be  treated as TE and
>> summarily discarded or prioritizes when table resources are scarce.
> Splitting the allocation can be done for many reasons. There are known cases where one LIR operates multiple separate networks, each with a separate routing policy. They cannot get multiple allocations from the RIR and they cannot announce the whole allocation as a whole because of the separate routing policies (who are sometimes required legally, for example when an NREN has both a commercial and an educational network). Deaggregating to /48's is not a good idea, but giving an LIR a few bits (something like 3 or 4) to deaggregate makes sense.

yes, that's my point for years now - probably filter /48s from allocations
(because end-users CAN get IPv6 PI assignments now everywhere i think), but do allow some
"sub-allocations" in the DFZ for such mentioned reasons. Because for the latter
there are no real "nice" solutions atm. (or probably update the policies to be able to acquire multiples
allocations without hassle in such cases, but OTOH it doesn't 
matter to the routing table, another prefix is another prefix)
It's much nicer to have, say, one /40 in the table aggregating some (routing-)separated /48 customers
than to have 200 /48 PI prefixes in that AS if each customer needs to get their own PI space if you
cannot split the allocation.

I thought that would be a good middle ground (combined with RIR RR based filters perhaps of course).

...but it seems like you even need to accept /48 from everywhere nowadays based on the
initial postings *sigh*
Not even I do like that, although i never was a big fan of strict filtering.
But it all comes down to this most likely, the internet is a distributed being, and RIRs
don't control routing. So /48 just will become the new /24 and some people will give us the good old "told you so!".

Mit freundlichen Grüßen / Kind Regards

Sascha Lenz [SLZ-RIPE]
Senior System- & Network Architect

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