IP Addresses for colocation

Hello NANOG,

I'm in the process of evaluating whether to transition away from self-hosting
web servers to have them hosted at a colocation facility. The obvious
advantages being greater capacities for bandwidth, power, cooling, and oh yes,
proper methods of putting out a fire (instead of drowning the servers in water
if they so much as overheat).

The concern I have is this: if we decide a few months down the road that we
don't like this particular colocation facility and wish to move to another one
across the street, I'd have to renumber all of my hosts. Is it possible to go
to any colocation facility with a block of IP addresses in hand and use them?
I'm talking about a /24 here, so I cannot request the addresses directly from
ARIN, rather I need to get them from some other source. I attempted to get
them from our current bandwidth provider, but they seem to be a little taken
aback by my request for a block of addresses that will not be routed by them
-- in fact, while writing this they called to tell me they will not provide IP
space unless they route to it.

Is there a better way to get a /24 that can "go anywhere"? Or should I just
justify a /24 at the colocation facility and go through the same process
should we decide to change? Is there a way to buy a routable /24?

Thanks in advance for any advice, on or off list. I will summarize unless the
answer is "you're crazy, such things aren't possible" in which case I'll be
off drowning my sorrows at a nearby watering hole.

Mark J. Scheller (scheller@u1.net)


Most answers centered around what was unfortunately a miscommunication on my
part. The actual host IP addresses are not going to change, as they are
NAT'd. So a lot of answers mentioned DNS and DHCP and other helpful things to
do so as not to have to renumber the host IP addresses. Fortunately, that
will not have to be done.

However, it looks like there is really no way to avoid changing DNS entries
for all the relevant domains every time we switch colocation facilities and
therefore IP addresses. Just remember to crank to refresh interval down near
"switching time" and hope not too many sites cache DNS entries longer than
they're told to.

The other summarization is that Sean is a curmudgeon and equally abusive to
most everyone.

Thanks to most everyone for helping and Sean for being a curmudgeon.

Mark J. Scheller (scheller@u1.net)