[lug] ip address bouncing

[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)

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.

> 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.

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've seen folks physically move their servers during these events,
however that raises the risk level of having a hardware failure to a
point where I don't recommend it.

> 
> Hugh
> 
> _______________________________________________
> Web Page:  http://lug.boulder.co.us
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-- 
Nate Duehr <nate at natetech.com>

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