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in-arpa zone for /27 subnet size

Discussion in 'Plesk for Windows - 8.x and Older' started by dwalford, Aug 24, 2007.

  1. dwalford

    dwalford Guest

    Our IP provider has delegated reverse DNS for PTR to our DNS servers.

    All is fine for /24 subnets but we are unable to resolve PTR requests if the IP is in a /27 subnet.

    Here is what the IP provider sent to us, i used to be able to implement it in Microsoft DNS but no in Plesk 8.1

    I am not able to create a zone in this format:


    Here is some guidance on setting up reverse DNS zones for IP subnets.

    Setting up classless in-addr files on your nameserver is slightly different than setting up a zone for an entire CIDR: /24 (255 IPs).

    Here is an example using a hypothetical subnet,, or, the first 128 IPs in this CIDR: /24.

    If you have 128 IP addresses in a particular block we would make the following entries into the CIDR: /24 zonefile on 'Verizon' servers:


    0 IN NS dns1.yourdomain.com.
    0 IN NS dns2.yourdomain.com.
    1 IN CNAME
    2 IN CNAME
    3 IN CNAME

    This points all queries for the first 128 IP addresses to a zone on your nameserver called

    The zonefile you create will look just like a normal zonefile (with PTR records etc.), only the zone file name will have a 4th octet noting the net address, or first IP in your subnet ......

    Here is a sample of what your zonefile should look like:

    1 IN PTR name.yourdomain.com.
    2 IN PTR host.yourdomain.com.
    3 IN PTR user.yourdomain.com.

    OR IN PTR name.yourdomain.com. IN PTR host.yourdomain.com. IN PTR user.yourdomain.com.

    For more info on subnetted in-addr on an NT machine you can also see the Microsoft website's white paper:

    Windows GUI may not let you edit the named.boot file manually, so this might not apply to you. If you are using BIND or a similar platform you should put the following directive into your named.boot file:

    primary db.reversefilename

    BIND named.conf would look similar to:

    zone "" {
    type master;
    file "";

    For more information about Classless IN-ADDR.ARPA Delegation, please see RFC2317. http://www.faqs.org/rfcs/rfc2317.html
  2. sergius

    sergius Golden Pleskian

    Nov 6, 2005
    Likes Received:
    Hello dwalford,

    Thank you for the report.
    Unfortunately you are right. Plesk does not allow manage reverse zone properly. However we are going to fix it in future versions.
    Now I only can suggest you to create it manually. Plesk will not touch it.