You're correct that it's several layers up with the failover. SMTP servers know 
how to do this - web browsers don't. You'd get about a 50% fail ratio if one of 
your two web servers was down in the listed config.

Thanks,
Brian Desmond
[email protected]

w - 312.625.1438 | c   - 312.731.3132

From: John Gwinner [mailto:[email protected]]
Sent: Thursday, November 17, 2011 7:18 PM
To: NT System Admin Issues
Subject: Redundant DNS

On our SMTP hosting provider, they have 'redundant' DNS entries for the same 
FQDN:

[C:\]nslookup server1.inboundmx.com
Server:  abc.xyz.local
Address:  192.168.253.254

Non-authoritative answer:
Name:    server1.inboundmx.com
Addresses:  216.82.253.99
          216.82.255.3
          216.82.242.99
          216.82.242.115
          216.82.250.115

My question to the group - can this general idea be used to create 'backup' web 
servers?

i.e.:

www.mycorp.com<http://www.mycorp.com> 1.2.3.4
www.mycorp.com<http://www.mycorp.com> 4.5.6.7

The way inboundMX described it, it was more of a load balancing thing.  I don't 
think a client stack will know to query DNS 'again' if the first IP address was 
down.

Is this kosher?

I couldn't see a way on the big registrars to have multiple "A" records anyway, 
so it may not be possible, but I thought I'd check.
                 == John ==
John Gwinner | Director of Technology
DAZSI /Oracle Business Applications
310.640.1300 (office) | 310.640.9900 (fax)
880 Apollo Street - Ste. 201 | El Segundo CA 90245

[Description: cid:[email protected]]<http://www.dazsi.com/>


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