Reverse DNS

Posted on 2007-08-01
Last Modified: 2008-02-01
Can you explain reverse DNS to me?
Question by:cpqt
    LVL 28

    Accepted Solution

    Normal DNS lookup translates a domain name like to an IP address (
    Reverse DNS does just the opposite, translates the IP address to the domain name ( ->
    Not that widely used but many email servers are set up to do a reverse DNS lookup to check that the sending domain indeed has the IP address it claims.
    Not all domain names have a corresponding reverse DNS record
    LVL 3

    Assisted Solution

    RDNS is just like what it sounds-  a DNS entry points a name ( to an IP address, well a reverse will say that points to  It's often use to verify mail is from who it says it's from on the message header.  

    see also:

    Expert Comment

    Reverse DNS allows you to provide an IP address and determine which hostnames are attached to that IP.  The zone file is typically in the format of  The 1.168.192 is the address in reverse of the subnet that you are using Reverse DNS for.

    A typical entry would look like:     PTR     somehostname

    If you reverse DNS lookup on it will return somehostname.
    LVL 3

    Expert Comment

    We all agree then.
    LVL 1

    Expert Comment

    Forced accept.

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