BCP: Slicing a /32 for an ISP

David Freedman david.freedman at uk.clara.net
Mon Apr 14 12:23:18 CEST 2008

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(Ignore the typo about two /48s making a /49 , too late to change that now!)

I started by carving my /32 into /35s, took one /25 for ourselves,
carved that into /48s, took one /48 for infrastructure, carved that into

I used /126 public addressing for transfer networks.


Steve Bertrand wrote:
| Quick to the point:
| Has anyone done any documentation on how they decided to slice up their
| IPv6 allocation?
| I'm pulling hairs deciding on a tactical solution for the long-term in
| regards to how I should 'cut up' my /32.
| Can anyone here provide any feedback, positive or negative to the way
| they have done this?
| What did you use for core infrastructure? What did you divide off for
| remote PoPs? Did you cut up your /32 into /35's and work from there? etc
| etc.
| I can't find any decent documentation for what has worked for an ISP,
| and how 'they' did it, particular to a small ISP. (forgoing an argument
| about CPE assignment, I just want to know how people are assigning and
| delegating routing slots from the core to their edge).
| Before I can make a concrete decision (because the size of the space
| still intimidates me), I've been simply using 'my:32::x/64' type
| addresses for testing within a single subnet.
| Regards,
| Steve

- --
David Freedman
Group Network Engineering
Claranet Limited
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