Moving networks

[Barry Margolin]

In article <bkv8vm$2u68$1 at sf1.isc.org>,
Jim McAtee <jmcatee at mediaodyssey.com> wrote:
>At what point in time should I update the IP addresses of NS1 and NS2 with our
>registrar (OpenSRS)?  Does it make any difference if this is done before the
>move, in anticipation of the 48 hour TTL on glue records, or should it be done
>only after the servers have been moved?

I suggest doing it before the move.  If you wait until after the move, then
you'll have very little redundancy until the registrar propagates the
change to the TLD nameservers, and things will still be spotty for a couple
of days while waiting for the old TTLs to expire.  If you do it the day
before the move, the change will propagate to the TLD nameservers that
night, but nameservers will continue to use the old, cached addresses,
which will work until you unplug the servers.  But some will time out the
cached entries and will be ready to start using the servers when you bring
them up in the new location.

>What else am I forgetting?
>
>One other complication.  We do a small amount of web hosting.  Several of our
>hosting customers have DNS served by other name servers.  What would be the
>best way to minimize downtime for their web sites?  Coordinating DNS changes
>for them at the exact time of our move (which will be on a weekend) is going to
>be a nightmare, especially since none of those customer's run their own DNS and
>have to request the changes through their ISP.

I'm not sure there's any painless solution.  The best you can do is tell
them the time that the move is happening, and ask them to tell their DNS
providers to reduce the TTLs the day before and update the A records at
that time.

If they can make their DNS entries be CNAMEs for names in your domain, they
wouldn't have to make any changes on their end.  This will work for their
www.<domain> entries, but if they want to have the domain itself point to
the web server they're screwed.

-- 
Barry Margolin, barry.margolin at level3.com
Level(3), Woburn, MA
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