On Fri, 25 May 2001, Scott Meyer wrote:
> I have a question about changing ISP's when a domain name(s) is registered
> to an IP address(s) owned by the ISP.
>
> Obviously, we need to get the DNS registration changed to an address owned
> by the new ISP. I have had some transitions that have not been real smooth,
> and would like the current best practice for doing this.
>
> Any input is apprectiated.
ObWhereDidItGo: Does anyone know where the "Ask Dr. DNS" web site went?
I wanted to point the poster to it, but couldn't find it. Oh well...
Just making sure I understand you right:
- You are the proud owner of domain bar.com.
- Some machine foo.bar.com is a public resource on your network, and it
is about to get a new IP address (or perhaps a group of machines is).
- You want to avoid becoming the proud owner of a giant headache.
In the procedure below, I'm going to assume that a 1-2 hour window from
the time you switch over the server and the time the last clients
elsewhere on the Internet see the new address is tolerable. Also, some
of the parameters below are arbitrary. Adjust as you see fit.
The key is to have direct control of the primary, or master, name server
for your domain. If you don't have that control, get it handed to you
ASAP. Well, perhaps not to you personally, but it should be controlled
by your organization, not by your ISP. Otherwise, you will most likely
have problems.
With that done, the rest is comparatively easy. Lower the minimum and
refresh times for your domain (in the SOA for domain bar.com, in my
example) and the TTL for the resources you're switching (the A for
foo.bar.com), in the weeks and days before the switch. Exactly when and
by how much, depends on the initial value. Assuming they were set to 1
week (a common value), you could set them to 24 hours 8 days before the
switch, then to 1 hour 36 hours before the switch.
When the time comes for the switch, change the address(es) *and the
serial # in the SOA*, and make your master server reload the zone. Check
that it loaded correctly, then have your slave servers get the zone from
the master. (Note: some of your slave servers may not be under your
control, and their admins may be reluctant to empty their dearly bought
name cache just for you. Don't lose too much sleep if that happens:
Thanks to the previous step, they will reload your zone anyway in at
most 1 hour, and most if not all clients will see the changes in at most
2 hours.) Test that clients go to the new address for the server.
Let it rest some time, say 24 hours, until you're sure the changes have
had time to percolate everywhere but to the more weirdly (and probably
incorrectly) configured name servers, then change the refresh and
minimum values on the SOA and the TTL on the A resource back to their
former values. Don't forget to change the serial # again. This time,
don't bother reloading your slave servers or bugging sysadmins. They'll
pick up on the changes soon enough without needing human intervention.
--
"Someone approached me and asked me to teach a javascript course. I was
about to decline, saying that my complete ignorance of the subject made
me unsuitable, then I thought again, that maybe it doesn't, as driving
people away from it is a desirable outcome." --Me
Message Posted at:
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