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Single domain, multiple IPs

Posted on 2009-03-30
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Last Modified: 2012-05-06
Hi,

Is there any way to configure multiple IP addresses within DNS for a single domain record? I have a client with an SBS server and this can be reached on two different IP addresses (primary and backup ADSL services). The normal way to do this would be with multiple MX records, but this is not possible here because mail is initially going through external spam fllter servers hence the MX records point there instead. Unfortunately the spam filter service has no automatic failover capability so I'm looking for a way to do this within DNS.

Is there way to configure host records such that a single URL (e.g. mailer.company.com) can resolve to multiple IPs? More importantly, can this be done in a way such that one address is primary and the other is only used if the primary is not reachable?

Tks.
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Question by:regisit
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Chris Dent earned 500 total points
ID: 24019308

Outside of the MX record, no.

While you can have multiple Host records for a single resource the DNS server won't care if one of those resources is down, it will continue handing out the IP address. Responses for resources with multiple records are rotated using Round Robin to provide a simple form of load balancing.

You may consider utilising an internet based service to modify the Host record should one system fail. It's still pretty basic, but at least it can be instructed to check the status of the service.

As an example, see:

http://www.netriplex.com/solutions/critical_dns/pricing_and_packages.aspx

Many more available if you google for "DNS Fail Over".

Chris
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Author Closing Comment

by:regisit
ID: 31564257
Thanks Chris, I'd just about come to the same conclusion. Preference would be to check Exchange so needs a way to check SMTP is up rather than the website. Seems EasyDNS has this capability.
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