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I want to know whether it is possible to configure website DNS (In Godaddy) to use two IP address. If the first one does not work, it has to take the second one.

I want to setup my Blog, email server, microblog in my PC. If the PC is shutdown, then I want the appengine/wherever I configure to take over so that service is not interrupted.

For example: blog.devsundar.com ==> First IP address is my machine IP. If it is not accessible it has to take my blogger IP.

Is this possible? Feel free to comment even if it is ridiculous idea.

Thanks in advance.

Cheers.

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3 Answers 3

It is a good idea, but as far as I know, it is not achievable that easily! You can have multiple DNS records for a domain; but when someone queries the DNS, first IP address received would be used. If, for example, the browser fails reaching the IP address for the domain, it will display a timeout error. Hopefully, next time you refresh the web page, another IP address will be received and contacted. In order to have "High Availability", solutions like "Linux Virtual Server" is a good choice, but it requires more work:

  • You will need a Virtual Server at the front (IP address of which is set in the DNS).
  • There can be as many web servers behind the Virtual Server as you want.
  • You may configure the Virtual Server to redirect requests to the first server as long as it is available, and use other servers if needed.
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Is there any public free service available for the same? (OR) I am thinking of using Appengine to do the redirection. GoDadyDNS record ====Points to====> Appengine AppengineCode checks for the availability and redirects to the appropriate IP. –  user39184 Aug 24 '10 at 11:02
    
Its just an idea, will have to experiment it. –  user39184 Aug 24 '10 at 11:03
    
It seems to be a good idea :) However, implementation details depends strongly on your servers! –  Amir Pakdel Aug 25 '10 at 5:45

There are several rough edges on that approach, even if the DNS/reachability issue is solved (among others):

  • Synchronization: It's quite hard to keep everything in sync and keeping it transparent to users (if not impossible) in a domestic environment. For example: The database connection used for the blog might not be accessible from outside GoDaddy's network for security reasons. Keeping a local db and syncing with Godaddy's won't work well.

  • Email: It should pretty much work if Godaddy's configuration tool let's you set it's mail server in store-and-forward mode (They might not let you do that kind of things).

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Failover is probably the worst possible way to provide fault tolerance. While I believe there are some extensions to the DNS system to support this - its still a bad idea even if they were supported by most clinets / DNS servers.

Is there a reason you can't use round-robin DNS entries (weighted to the "primary" server)?

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