using "reserved" IPv6 space

Owen DeLong owen at
Tue Jul 17 04:26:00 UTC 2012

You could try this:

If you give a /48 to each site, then assign the sites primary and backup firewalls.

Aggregate the /48s into larger blocks by primary firewall.

Aggregate the primary firewall bocks into larger backup firewall aggregates.

Advertise the firewall-specific aggregates and the less specific backup-firewall set


On Jul 16, 2012, at 7:04 PM, Lee wrote:

> On 7/15/12, John Levine <johnl at> wrote:
>>> I feel like I should be able to do something really nice with an
>>> absurdly large address space.  But lack of imagination or whatever.. I
>>> haven't come up with anything that really appeals to me.
>> Use a fresh IP for every HTTP request, email message, and IM.  Just think of
>> how well you can do error management.
> hrmm...  nope, can't think of a single thing.  Then again, I'm on the
> routing & switching team at work, so things like HTTP requests, email
> messages, and IM are just different types of user traffic that needs
> to be routed to me.
> Recall the message I was responding to:
>>>> There is a HUGE difference between IPv4 and IPv6 thinking.  We've all
>>>> been living in an austerity regime for so long that we've completely
>>>> forgotten how to leave parsimony behind.  Even those of us who worked
>>>> at companies that were summarily handed a Class B when we mumbled
>>>> something about "internal subnetting" have a really hard time
>>>> remembering how to act when we suddenly don't have to answer for every
>>>> single host address and can design a network to conserve other things
>>>> (like our brain cells).
> I read it as design a network >>addressing scheme<< to conserve other
> things & was hoping someone could share new ways of looking at it.  I
> feel like I'm stuck in "IPv4 think" with an addressing plan that's
> basically
> Each site gets a /48.  Even the ones with less than 200 people.
> Each subnet is assigned a /64 except for loopbacks & p2p subnets.
> First 256 subnets in each /48 are reserved for things like loopback
> addresses, p2p links, switch management subnets, etc.
> High order 4 bits of the site address are used for the subnet type.
> So a /52 tells you the site and if it's users, printers, servers, IP
> phones, or whatever.
> Which is *boring*.  Nothing novel, no breaking out of "IPv4 think"
> aside from massively wasting address space.  Which brings me back
> around to my original request for suggestions.  What's the new way of
> looking at designing a network addressing scheme?
> Regards,
> Lee

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