ISP customer assignments

Tue Oct 6 14:21:08 UTC 2009

> -----Original Message-----
> From: William Herrin [mailto:herrin-nanog at dirtside.com]
> Sent: Monday, October 05, 2009 12:58 PM
> To: Brian Johnson
> Cc: nanog at nanog.org
> Subject: Re: ISP customer assignments
> 
> /60 - the smallest amount you should allocate to a downstream customer
> with more than one computer. Anything smaller will cost you extra
> management overhead from not matching the nibble boundary for RDNS
> delegation, 

I have a lack of imagination, I guess.  I can't imagine anyone larger than
a small residential user being assigned a /60 or less.  Therefore, 
nybble boundary for rDNS delegation only matters if you delegate
rDNS for that block.  

> handling multiple routes when the customer grows, not

Any customer getting a /60 or less will be dynamically numbered
(RA, DHCPv6, whatever), and if more space is needed, should be
easily renumbered into a larger prefix.

> matching the standard /64 subnet size and a myriad other obscure
> issues.

I don't know about "myriad" but I agree that /64 is the standard 
subnet size.

I am *not* advocating assignments of /60 or less, just pointing
out that if you do it, it doesn't have to break.

Lee