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DNS multiple A records/CNAME query

Posted on 2010-08-26
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Hello

We are running Windows 2003 AD DNS - domain is company.com

We have a web application that we want to be accessed on http://webapp.company.com

The actual application will be running on two Windows 2003 Servers - server1.company.com and server2.company.com

Does anyone know how I can make "webapp.company.com" point to both servers (for load balancing)?

Do I:

i. Create an A record for 'webapp' have it point to the IP addresses of server1 and server2

ii. Create a CNAME entry of 'webapp' for the A records of server1 and server2?

iii. Something else?

Also - do I need to make the PTR records point back to 'webapp'?

Secondly, I would also like to implement some sort of fault tolerance here. So that if, say, server1 was down, all requests would go to server2.

iv. Am I correct in thinking that the solution I implemented for DNS load balancing above would not help? Even if a server was down, DNS would still return either address for requests?

v. What I need is a load balancer (Cisco etc)?
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Question by:Joe_Budden
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anomiagrunge earned 500 total points
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You should use Network Load Balancing.
You publish your webapp on the virtual ip of the cluster an all the balancing and the failover works automatically.
Start by reading this: http://technet.microsoft.com/en-us/library/cc758834%28WS.10%29.aspx

Hope it helps

Ariel
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by:Joe_Budden
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Thanks!

Out of interest, if I only wanted to use DNS round robin, how would this work in terms of the DNS entries (questions i and ii)?
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by:MojoTech
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It won't really afaik, you need to configure load balance or cluster failover.
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by:anomiagrunge
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In that case, just configure 2 A records with the same name pointing to the different servers. It only will balance the load on a 50-50 basis.
Be aware also that if your app keeps session of the client, you need to maintain it and that can´t be done with DNS.  
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by:Joe_Budden
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Thanks - so for purely round robin, I couldn't do any of these:

i. Create an A record for 'webapp' have it point to the IP addresses of server1 and server2

ii. Create a CNAME entry of 'webapp' for the A records of server1 and server2?

I would need to create two seperate A records, and have each one point to the IP's of server1 and server2?
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by:anomiagrunge
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You can´t create an A record pointing on 2 addresses. The only way is to create 2 separate A records with the same name pointing to each server
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by:Joe_Budden
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Thanks...

What is wrong with (ii) [the CNAME idea] too? Just so I know the reason I am wrong :)
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by:anomiagrunge
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You can also do the same i told you with CNAME´s. It´s the same.

Regards!
Ariel
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