I just went through all this myself. I'm not a cable modem provider, so
the rules may be slightly different.
In the beginning, I had SWIP'd records. However, as most net admins, I
had fallen way behind on this. Here's what I did to rectify my problem:
a) Created a spreadsheet listing parent CIDR delgations from our
upstream. Broke those out into subnets that we delegate to customers,
ping scan them periodically, and get a max utilization. Sum your total
current space and max usage, get a percentage. So long as the company
holds 1 ip over a /19, they are eligible for a /18 AFAIK.
b) Apply for an ASN at this point. Tell ARIN you are going to be
multihoming, and can provide signed contracts with ISP's proving this.
Without multihoming, you don't need an ASN -- your upstream should be
more than happy to announce your address space for you later on.
c) Take all that spreadsheet data, and throw it into an rwhois server.
For a /20 worth of addresses, this took me the better part of 3-4 days
of data entry. I would expect it would take one person 12-16 days for a
/18 worth of addresses. Need it faster? Throw more people at data
d) Get your rwhoisd server up and running. By this time, you should
have your ASN number (took us about 1 week). Fill out the IPv4 request
template. Send it in. After a day or two, they'll email you back
asking you a few things about your policies on how you decide how many
IP's a customer gets. I think that they just want to hear the policies
that they have on their website (i.e. target 80% utilization within 3
months). 1 week later you should have an allocation.
e) Start migrating stuff over. When you make delegations in your new
/18, put them in your rwhois server. You'll need it when you go back to
ask for more address space in a year, and why go through all this stress
more than once.
If they give you grief about a /18, ask for a /19 and ask them to
"reserve" the other /19 space within a /18. Prove to them that you are
effectively utilizing the /19 and they'll probably give/sell you the
Someone else here mentioned that the folks at ARIN are truly helpful --
They are. I emailed them a few times asking for clarification on some
of the forms, and I had answers within the hour.
My $0.02, and I just turned up my ASN and my netblock today!