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Thread: Reverse DNS

  1. #1
    Join Date
    Jul 2005
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    india
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    Reverse DNS

    Hi ALL,

    I have a dedicated server so do i need setup reverse dns for my dedicated server or it will be automatically setup by my host.

    If i have to setup by myself how i can do that?

    I have to setup reverse dns on domain that i am hosting on that server or i also need to put reverse dns for my dedicated server?

    Please help me.

  2. #2
    Join Date
    Oct 2003
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    Hanoi
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    4,306
    You will need to ask your provider. They will do it with their upstream

  3. #3
    Join Date
    Mar 2004
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    Singapore
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    How many IPs do you have? If it is a lot maybe a class c, ask your provider to delegate the IPs to you, you can then do the reverse DNS yourself. If not you need to ask your provider to reverse them for you.

    Some companies do this automatically, check if your IPs are already reverse using http://www.dnsstuff.com/

  4. #4
    Join Date
    Jul 2005
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    india
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    i have 4 ips for my server.Is there any way i can do reverse dns by myself or i have to ask my host to do this?

  5. #5
    Join Date
    Feb 2003
    Location
    Cambridge, UK
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    For 4 IPs your host needs to do it for you.

    The minimum delegation size for reverse DNS zones is a Class C (i.e. 24-bit) subnet.

    Some hosts allow you to update these yourself via a control panel or similar on their own systems.

    Regards,

  6. #6
    Join Date
    Jul 2005
    Location
    india
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    No you are getting me wrong i have 4 ips means one is dedicated for server other 2 is working as dns and one is free. Can i use that free ip for reverse dns for my server?

  7. #7
    Join Date
    Feb 2003
    Location
    Cambridge, UK
    Posts
    33
    Sorry, I'm not with you.

    You don't need to allocate an IP address for reverse DNS. Reverse DNS is simply a reverse name mapping for each of your existing IP addresses (i.e. you can have 1 reverse entry for each of your 4 IPs).

    Reverse entries allow "nslookup <ip address>" to return the FQDN assigned to that IP.

    Regards,

  8. #8
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    Jul 2005
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    india
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    SO means i can't do this by myself. I have to take help of host.??

  9. #9
    Join Date
    Sep 2002
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    Originally posted by applepanther
    SO means i can't do this by myself. I have to take help of host.??
    Firstly,
    No matter HOW many IP addresses you have for your server, you must have your DC set this up, unless you maintain control of your IP space, and you own the ip addresses. The only ones authorized to make said change are the individual ip owners, which means that it's got to be done by the DC.

    Secondly,
    All you really need to have setup with RDNS is one, that would be the base ip of your system (usually). Here's why:

    No matter what application comes out of your system, it'll all be processed through the base ip of your system, unless you've specifically told the application (ie: exim) to bind to another ip address.

    The only place that RDNS truly matters is your MTA. Since your MTA sends mail OUT as the base ip , the only IP address you need to have configured with RDNS is your base ip address.

    Make sense? Hopefully If not, ask questions
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  10. #10
    Join Date
    Feb 2005
    Posts
    334
    Just to make the point, though in general yes your host will do reverse DNS for you a smaller than /24 allocation can be delegated. In general its much easier to just have a host do it for you though. Do a google search for "classless subnet reverse delegation" and you will see what I mean.

  11. #11
    Join Date
    Jan 2005
    Posts
    2,175
    Also better to have a rdns entry since some mail servers reject IPs that doesn't have one such as AOL.

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