Redirecting IP temporarily

I thought I had this figured out, but I've received mixed information
in recent weeks. I'd appreciate it if someone can tell me if this can
easily done.

My problem is I need to move a server to another provider with little
downtime.

What I want to do, is change my DNS records to the new IP set. Next,
I would place a Linux box at the new location that would re-direct the
packet to the old server location. Once the new IP's resolve, I'd
then move the actual boxes to the new location, and stop the
forwarding service on the Linux box.

My concern deals with downtime of both web and email services, so the
idea would need to work with both. As for DNS, I already plan to have
two DNS servers at each location to handle each side. Any ideas?
Thanks!

Bob Wiley

On 23 Sep 2003 11:35:11 -0700, Robert H. Wiley <(E-Mail Removed)> wrote:
> I thought I had this figured out, but I've received mixed information
> in recent weeks. I'd appreciate it if someone can tell me if this can
> easily done.
>
> My problem is I need to move a server to another provider with little
> downtime.
>
> What I want to do, is change my DNS records to the new IP set. Next,
> I would place a Linux box at the new location that would re-direct the
> packet to the old server location. Once the new IP's resolve, I'd
> then move the actual boxes to the new location, and stop the
> forwarding service on the Linux box.
>
> My concern deals with downtime of both web and email services, so the
> idea would need to work with both. As for DNS, I already plan to have
> two DNS servers at each location to handle each side. Any ideas?
> Thanks!

Change the DNS expire time to be short sometime before the changeover to
give the short expire time, time to propegate. For example if your old
expire time was 2 days, shorten the expire time at least 2 days before the
changeover (to give cached DNS time to flush). For example, I use dynamic
DNS with 60 sec expire time (no-ip.com), so if my IP changes, the name
follows it almost immediately.

Then after the move, set the expire time back to normal.

Of course if changing nameservers, there will be a lag from the time you
notify your registrar until it takes effect in the root servers. But if
you control both sets of nameservers, and they have the same data, that
should be transparent.

For web you could set up the old server to proxy the new server by IP (see
apache docs for mod_proxy and ProxyPass).

Mail can be relayed from the old location using the new IP in square
brackets. But users who want to use pop3/imap may have to temporarily
use the new server IP until DNS propegates.

But if you plan ahead and do the short DNS cache expire thing and
move in early morning hours, the changeover should go as quickly as
you can transfer everything to the new location.

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