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DNS Virtual Hostname or Multihomed?  How to set this up...

Posted on 2009-07-13
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Last Modified: 2012-05-07
I am kinda weak in my DNS experience, I need help setting something pretty simple up.  DNS is running on Win Server 2003.

I need a hostname to use two IP addresses for redundancy.  I have a load balancer application that could benefit from this.  I have two machines, one is a primary server and the other is the backup.  If the primary goes down, I want the backup to respond to the same name.  I know the clients will timeout on the primary when it goes down, but at least after awhile they'll be able to reconnect to the backup if DNS redirects them to the correct IP.  I don't think it matters which server they are using if they are both online, what I need is for one of the two to always be available.

common DNS name: JPLTS0

Primary Server: 172.16.7.175
Backup Server:172.16.7.113

What steps do I need to do in DNS management to make this possible?

Thanks..
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Question by:jamietallman
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by:Chris Dent
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DNS won't care if your services are up or down.

If you need it to respond with a specific IP depending on service state you need to remove the down address from the DNS system entirely. Typically this means having something monitor the service, then make changes in DNS if the service state changes.

Chris
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by:jamietallman
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I wondered how DNS would figure this out.  I guess it won't.  Do you recommend a way to monitor DNS service?
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by:Chris Dent
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It's the application you need to monitor rather than DNS. Do you have any monitoring software in place at the moment? If something can tell when the service breaks it may be possible to have that fire off a script and make changes in DNS.

Chris
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by:jamietallman
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So i could monitor it with pings to see if the machine is down, then if it is, programmatically change the DNS entry to the backup IP address or vice versa.

I was really hoping to not have to do something custom like that, but I suppose I could.  
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Chris Dent earned 125 total points
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Yep, that would do.

Your choices for changing the record are likely to be DNSCMD or WMI. WMI is more flexible, but a bit more effort than DNSCMD. For DNSCMD you would be removing the record and adding a new one (or just removing depending on the situation).

Chris
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