[ppml] Increase the flexibility of IP allocations to facilitate planning

jlewis at lewis.org jlewis at lewis.org
Wed Jul 23 11:15:24 EDT 2003

On Wed, 23 Jul 2003, Leo Bicknell wrote:

> > used/assigned/allocated...not how much of the space is actually in use by
> > devices, as long as you're being reasonable (following ARIN guidelines) with

> Not quite.  If you get a /23 (to make numbers easier) and allocate
> 4 customers /25's, but each customer only needed 4 IP's your not
> going to pass ARIN's muster, even though you've "assigned" > 80%

Yeah...that wouldn't be reasonable or inline with ARIN guidelines if you 
assign each customer many times more IPs than they think they may ever 

> of your IP space.  The rules are transitive, and apply down stream
> as well.  If you assign IP's to a customer, they must also meet the
> 80% rule.

See RFC2050, sections 3.0 and 3.1.

I'm beginning to suspect you've never actually personally dealt with ARIN 
for the purpose of obtaining an IP allocation.

> Problem is, if you have a customer with 7 devices (say, a small
> office) you have to assign them a /28 for their lan, at 56.2%
> utilization (7 + 2) / 16.  Now, what happens if you get a /23, and
> end up with with 32 customers, each with 7 devices.  You've "assigned"
> 100% of your IP space, but only 56% of your IP space is in use.  By
> the letter of the rules I don't belive you meet the 80% rule, yet
> you can't do any better.

If you're assigning customers the smallest subnets the can fit into, the 
wasted IPs are irrelevant, and you've utilized the space in accordance 
with ARIN's rules.  % actual usage does not matter.

 Jon Lewis *jlewis at lewis.org*|  I route
 System Administrator        |  therefore you are
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