[lug] ip address bouncing

[Nate Duehr]

Hi Hugh, 

Well the answer is too late to help you out, but the folks I've seen who
needed to have old servers on the old IP's just used HTTP REDIRECT to
send the traffic to the new site.

Hopefully your move went well!

Nate

On Mon, Oct 22, 2001 at 07:52:21PM -0400, Hugh Brown wrote:
> "Nate Duehr"
> > 
> > Thoughts below...
> > 
> > On Mon, Oct 22, 2001 at 09:43:45AM -0400, Hugh Brown wrote:
> > > We are having a weekend long power outage where I work and I need to move a
> > > box to another location.  I am trying to minimize the amount of time it
> > > takes for dns to update.  
> > 
> > Bummer.  Need to move your computers to a data center!  :-)  (Blatant
> > plug for my employer here.. heh)
> 
> DC to CO is a bit more traumatic a move than a mile down the road :)
> 
> > 
> > Minimizing DNS downtime is a direct relation to turning your TTL time
> > down at least 2*TTL in advance.  If your DNS TTL time is longer than a
> > week, you're already hosed if the outage is planned for this coming
> > weekend.
> > 
> > > Is it possible to take the old ip address and redirect all traffic destined
> > > to it to a different address?
> > 
> > Only if something is still answering on the old IP address.
> 
> I am doing the move on wednesday evening. so I have all day thursday and
> friday to have something answering on the old ip address.
> 
> How is this traffic redirect done?
> 
> > 
> > > If a have two A records for a host and the first ip isn't available will
> > > the second ip be tried or will the process return a host not
> > > found/unavailabe?
> > 
> > Multiple A-records officially are handled however the resolver wants to
> > handle them.  In practice, they round-robin.  So by adding another A
> > record with another IP, 50% of the people coming to your site will get a
> > failure on the first try, and have a 50/50 chance of hitting the "up"
> > site every time they hit refresh.  There's a rather large warning
> > against using DNS for load-balancing in the DNS FAQ at www.isc.org --
> > and this is why.
> 
> That's what I thought.  Just wanted to be sure.
> 
> > 
> > I recommend you get your TTL time turned down immediately, and get
> > another "mirror" server ready to handle ALL your traffic at another site
> > so you can just point your DNS there during your downtime.  That's the
> > cleanest way to do it.  Also, don't forget to consider where your DNS is
> > hosted.  If it's hosted at the site that is going down and there's no
> > off-site slave configuration you'll have an awfully hard time getting
> > anyone to your site at all.
> 
> I turned it down to an hour from two days so I might be able to manage it.
> 
> One of the authoritative hosts for the domain is offsite so I should
> hopefully be okay.  We'll see how it all turns out.  Worse comes to worse,
> we tell people to point at an ip address.
> 
> Thanks much for the help.
> 
> Hugh
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-- 
Nate Duehr <nate at natetech.com>

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