Linux as backup (failover) machine

[Brian Cluff]

The biggest problem with this no hardware/nosoftware method is that it's not
all the perfect.  Stupid networks like @home have decided not to honor the
cache times of DNS records.  I found this out the hard way when moving an
ISP's machines to be new network.
 I had sevral weeks before changed the timeout to 15 minutes in preparation
for the move.  The move went incredible smooth and I expected no large
snags.  Then days later I couldn't get to our web page though cox and I had
dozens of reports of e-mail. cox and non @home customers, couldn't get their
mail to our servers.  It was about 3 weeks before  things were back to
normal.   So, the below solution would work, but it wouldn't be for 100% of
your traffic.

Brian Cluff
----- Original Message -----
> Got access to modify your DNS?
>
> On the primary nameserver for the domain(s), try connecting to your
> webserver. If no connection, change the DNS to point to your Linux box via
a
> shell script. On the slave nameserver, just don't keep a local copy of the
> domain record(s).
>
> To be more careful and to prevent 'accidental' network hiccoughups, this
is
> what i'd say to my boss:
>
> 1. shell script that pings webserver
> 2. if ping doesn't respond, open a connection on port 80 of your webserver
> 3. if connection fails, run a script to alter DNS (change ip of your
> webserver)
>
> ICMP. If this doesn't work, it may not be there after all, but try TCP/IP
> just to be absolutely sure it's not there. If TCP/IP isn't working, then
> changeover to the linux box.
>
> Problem is, you'll need to change the caching times for your domain(s)
> unless you don't mind longer expiration times. But, this would be extra
work
> for your nameserver(s).  =(
>
> No hardware and no extra software. =)
>
> marco
>
> -----Original Message-----
> From: plug-discuss-admin@lists.PLUG.phoenix.az.us
> [mailto:plug-discuss-admin@lists.PLUG.phoenix.az.us]On Behalf Of Ken
> Bowley
> Sent: Friday, November 03, 2000 6:12 PM
> To: PLUG Discuss
> Subject: Linux as backup (failover) machine
>
>
> Hello everyone!
>
> I've been posed with a question, and I'm a little stumped... please bear
> with me.
>
> Problem:
> Make a Linux machine automatically kick in as a failover machine for http
> when the NT machine goes down.
>
> Restrictions:
> Need to be able to monitor the NT box without installing anything extra on
> the NT machine.
> Linux machine needs to be able to kick in automatically when the NT box
goes
> down, and give control back to the NT box when it comes back up.
> No access to installing any type of router/proxy between the NT and Linux
> box and the rest of the net.
>
> Please send your ideas either directly to myself, or to the list if this
> problem is of interest to others.
>
> -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= O-
> Ken Bowley/SysAdmin            mailto:johann@vikingsystems.com
> Viking Systems, Inc.              http://www.vikingsystems.com
> -=-=-=-=-=[Sair Linux and GNU Certified Professional]=-=-=-=-=-
>
>
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