[157249] in North American Network Operators' Group
Re: Is a /48 still the smallest thing you can route independently?
daemon@ATHENA.MIT.EDU (Jimmy Hess)
Thu Oct 11 19:12:03 2012
In-Reply-To: <CAP-guGVB6FbxYcZFJ2EzKyue3rZ=by=ttZHodtwQ3yDHOKC1vA@mail.gmail.com>
Date: Thu, 11 Oct 2012 18:11:50 -0500
From: Jimmy Hess <mysidia@gmail.com>
To: William Herrin <bill@herrin.us>
Cc: nanog@nanog.org
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
On 10/11/12, William Herrin <bill@herrin.us> wrote:
> On Thu, Oct 11, 2012 at 6:06 PM, Randy Carpenter <rcarpen@network1.net>
> wrote: >> How many sites do you have? If less than 192, /44 is
>> perfect, unless some of those sites require more than
>> a /48. Then, it gets more complicated :-)
>
> We're having a general math breakdown today. First Jeroen wants to fit
> 5 /48's in a /47 and now you want to fit 192 /48's in a /44.
> 48-44=4. 2^4=16.
Right, last I checked the smallest integer >= Log base 2 of 5
is not less than or equal to 1, therefore, you will never fit 5
/48s in the network just by subtracting 1 from the prefix length.
if you want a prefix /yy that will accommodate a certain number
N of /xx
Then you must ensure that
2^(xx - yy) >= N
not
5^(xx -yy ) >= N
>
> -Bill
--
-J
