# Is a /48 still the smallest thing you can route independently?

I've finally convinced \$DAYJOB to deploy IPv6. Justification for the IP space is easy, however the truth is that a /64 is more than we need in all locations. However the last I heard was that you can't effectively announce anything smaller than a /48. Is this still true?

Is this likely to change in the immediate future, or do I need to ask for a /44?

He said it was for multiple sites. Per ARIN policy, the next biggest chunk from a /48 is a /44, so a /44 is what should be asked for. It is perfectly justifiable if you have more than 1 site.

I would not expect anything smaller than a /48 to be allowed in BGP.

A bonus would be that a /44 currently costs the same as a /48 for an enduser, so there really is no drawback from getting the /44, and having enough space to not have to worry about it in the future.

-Randy

It's only a worry if you can only route /48s, which was my question. And seriously, we're going to be banging around in the emptiness as compared to our IPv4 allocations.

You can route /48 or shorter (larger)

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

-Randy

A /44 would give you 16 /48s. If you have 192 sites - assuming a /48 per site - you would want at least a /40.

jms

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.

-Bill

Wow and I thought nibble boundaries would make the math easier than HD ratios.

Here's the breakdown for those who are mathematically challenged:

n sites prefix
0 Nothing.
1 /48
2-12 /44
13-191 /40
192-3071 /36
3072-49,151 /32
49,152-786,431 /28

If you're managing more than 786,431 sites, then you should be able to afford
to hire someone who can properly handle the math.

Owen

Yep... I don't know why, but I was thinking /40.

So,

1 site = /48
2-12 sites = /44
13-192 sites = /40, and so on.

NRPM 6.5.8.2 for details.

/40 bumps you into the next price category, but it is a 1-time expense for endusers.

-Randy

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