Use DHCP, get your customers to use DHCP. Current Best Current Pratices
for IP allocations (http://ftp.fc.net/rfc/rfc2050.txt) states:
5. Due to the requirement to increase the utilization efficiency
of IPv4 address space, all assignments are made with the
assumption that sites make use of variable length subnet mask
(VLSM) and classless technologies within their network. Any
request for address space based on the use of classfull
assumptions will require a detailed justification. The use of
classfull technologies for the purposes of administrative
convenience is generally insupportable due to the limited
availability of free IPv4 address space.
While it is understood that the use of static addressing may
ease some aspects of administration, the current rate of
consumption of the remaining unassigned IPv4 address space does
not permit the assignment of addresses for administrative ease.
Organizations considering the use of static IP address assignment
are expected to investigate and implement dynamic assignment
technologies whenever possible.
This means that you should use renumbering technology as much as
possible, so that when you can justify a /19 you can get one,
until then, find an ISP that is multi-homes and can provide you
the IP addresses you need, and consider two connections to them,
giving you the benefit of being multi-homed without the cost of
the routers needed for full BGP, or needing to justify a /19.
This is all great and dandy, but then why does it appear that anybody with
a cable modem this side of the sun are using static IP's. Granted that
the Nic probably didn't allocate the current /8 (or the next one), but I
don't see any (and didn't see any prior) 'investigation' to make dynamic
allocation possible (or using RFC1918 addresses). Are they looking at
DHCP or RFC1918 as a solution for their userbase ?
While we're here pulling our teeth on returning addresses and not
allowing static IP's for a combined user base of several million internet
users, a group of users with less than 50K (correct me if I'm wrong here)
and no track history of rwhois/swipped addresses gets gets /8's for
allocation to a static IP userbase.......
We're doing cablemodems out of RFC1918 address space using PIXes in
several communities and it hasn't been fun. Many of the latest-n-greatest
network apps (games, video, voice, what have you) are broken by NAT. They
seem to like to transmit the client's address at the application layer.
This of course doesn't work, since the client's address is 10.x.x.x...
You can dismiss this problem by saying the apps are broken (which they
are), but the simple fact is our customers want to use these apps.
I'd recommend DHCP. In communities where we've used it, it has worked
fine and not caused any of the problems that NAT does.
Thanks for your comments. What sort of DHCP lease times do you use? What
kind of ratios between customers and IP addresses work in your situation?
In other words, I'm looking for how much more IP space, if any, you need
versus the dynamic IP assignment we're used to seeing in dial up ppp service.
Larry Vaden, founder and CEO help-desk 903-813-4500
Internet Texoma, Inc. <http://www.texoma.net> direct 903-870-0365
bringing the real Internet to rural Texomaland fax 903-868-8551
Member ISP/C, TISPA and USIPA pager 903-867-6571