"Recommendations on IPv6 Route Aggregation" (was: Re: IPv6 multihoming)

Pekka Savola pekkas at netcore.fi
Wed Feb 9 07:32:37 CET 2011

On Tue, 8 Feb 2011, Rob Evans wrote:
>> Rob, please correct me if I have missed the more recent version of this
>> document.
> You haven't.  Equally there isn't that much to document, although
> curiously this is now the fourth time this has come up in the last
> couple of weeks.
> In my experience the number of people filtering on /32s appears to be
> diminishing, /48s are widely accepted (for unverified values of
> "widely"), and so "prudent subdivision" of a /32 is likely to become
> the norm where needed, especially as the proposal to allocate
> additional /32s for routing reasons did not reach completion in the
> RIPE region.

I would take the following into account in revision:

Whether you accept /48 is not a one-bit decision.  Specifically:

- quite a few still filter more specifics from PA ranges
- quite a few still reject /48's set aside for IX fabrics
- almost everybody accepts /48 (or sometimes shorter) in designated PI 

So, if you do break a PA /32 block down to smaller pieces, you should 
expect some to filter more specifics.

BCP in this field should include a statement that (also per address 
allocation policy), the whole aggregate MUST still be advertised as a 
single prefix even if you advertise more specifics. The onus is on the 
advertiser to make sure connectivity works to to the subblocks through 
the aggregate.

Pekka Savola                 "You each name yourselves king, yet the
Netcore Oy                    kingdom bleeds."
Systems. Networks. Security. -- George R.R. Martin: A Clash of Kings

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