BCP: Slicing a /32 for an ISP

Michael Adams madams at netcologne.de
Tue Apr 15 15:30:35 CEST 2008

Mark Tinka,  14 Apr 2008 15:57:

> > I'm eager to hear more opinions about this. We are going
> > to use /64 for all kind of network interfaces including
> > point-to-point links and loopback interfaces.
> We saw no point in using /64 especially for point-to-point 
> links and Loopback interfaces.

There is one statement I heard more than once when talking about
IPv6: Be wasteful. No problem for me. I wish my boss would say
something like this ;-)

For me one reason for /64 is, I don't know what future brings. 
Right now there are only a few reserved addresses. If you have 
started with /126 you might have a problem now. I also don't know 
what hardware optimizations some vendors will implement one day 
which are based on /64 boundaries. So currently I'm going for /64 
because I'm considering it as safe (and simple). 

I also like the idea using link local addresses on router transfer
links only. So one could safe even the /126 net's. But I would
like to have public addresses with proper reverse lookups (for
tracroutes for example).

Another point I'm thinking about is: what shall I give to our residential
custumors? A /64 would be sufficient for most of them as there is 
usually only one PC/Mac. A /56 would match every constellation I can
imagine today. A /48 would fit the 'No questions asked' rule. So
why not a /48 for every residential custumer? Or is this to wasteful?


Michael Adams                             Tel: +49 221 2222 657
Network Engineering & Design              Fax: +49 221 2222 7657

NetCologne                                Geschäftsführer
Gesellschaft für Telekommunikation mbH    Werner Hanf
Am Coloneum 9                             Dipl.-Ing. Karl-Heinz Zankel
50829 Köln                                HRB 25580, Amtsgericht Köln

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