Thread: Split DNS

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    Split DNS


    I used nslookup to fetch the ip address of one website, say google, but get different responses sometime (need to wait for sometime and resolve again). I thought it could be split dns feature but my ip wasn't changed when I tried to get the ip address. So what function/technology is it? Is this split dns or other feature?
    Actually, this strange feature cause some issues on my program and I want to setup a similar function on my machine(ubuntu + bind9) to debug, but I don't know how to do it.

    Thanks

    Jay
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    It's a load balancing feature of the DNS server called round robin.
    PHP FAQ

    Originally Posted by Spad
    Ah USB, the only rectangular connector where you have to make 3 attempts before you get it the right way around
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    Originally Posted by E-Oreo
    It's a load balancing feature of the DNS server called round robin.
    Thank you for your reply, but it looks like different. Round robin gives same ip list but different orders. What I got from the server were totally different ip list.
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    There is no reason a server can't return a different list when implementing round robin, especially for a company the size of Google where it would be utterly impractical for their reply to actually contain all of their server IPs.
    PHP FAQ

    Originally Posted by Spad
    Ah USB, the only rectangular connector where you have to make 3 attempts before you get it the right way around
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    Agree what you said, but how to do that? I configured 6 ip address for one host name in Bind9, but the server response all of them.

    Here is the configuration and result:

    www IN A 172.16.0.93
    www IN A 172.16.0.94
    www IN A 172.16.0.95
    www IN A 172.16.0.96
    www IN A 172.16.0.97
    www IN A 172.16.0.98


    Server: UnKnown
    Address: 172.16.0.172

    Name: ( address blocked: See forum rules)
    Addresses: 172.16.0.93
    172.16.0.94
    172.16.0.95
    172.16.0.96
    172.16.0.97
    172.16.0.98


    Do you know any configuration or any dns software has the similar function as google (return part of ip addresses) which I could setup on my machine?
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    Comparing BIND to Google is a bad idea in this case since they don't use BIND and don't seem to always follow rfc's. They use in house DNS software. It's not bad but you can't really compare it with most things out there. There might be some software you can use for that but nothing I can think of.

    Standard DNS returns all of the resource records for a query of that type(should be somewhere in rfc 1035 or 34). By default, BIND will mix up the order it responds and most clients will just use the first one they see.
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    I'm not actually sure how you would configure a server to do that, I just know that it's possible to do from a technical standpoint. (In general I try to avoid manually configuring name servers and mail servers.)
    PHP FAQ

    Originally Posted by Spad
    Ah USB, the only rectangular connector where you have to make 3 attempts before you get it the right way around
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    Thanks for you guys. I have a clear understanding about this issue now. Maybe I need to write some scripts to simulate the behavior of google.

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