reverse dns records, standard delegation and classless delegation

fyi: managed dns services -

  • reverse dns records, standard delegation and classless delegation

    Reverse DNS records permit the lookup of the host name corresponding to an ip address. Direct management of the mapping of host names to ip addresses requires that control of the reverse zone be delegated to the managing party.

    The two forms of delegation are standard delegation on a standard subnet boundary and classless delegation by means of CNAME records. (see rfc 3172) edgedirector name servers can handle both types of delegation as long as the correct delegated zone name is specified.

    In either type of delegation, the records are kept in a separate dns zone ending in

    In practice:

    • A standard delegation on a subnet boundary uses the standard name. The delegating name server simply returns a referral to your dns server.

    • A classless delegation will also end in but are preceded by the delegation naming convention used by the upstream party granting the delegation. The delegating name server contains cname records for each individual address and returns a referral to your dns server and the appropriate cname record contents. There are several recommended naming conventions. The correct one to use is determined by the delegating name server.

    zone name examples

    zone name for standard delegation of
    zone name for classless delegation of
        subnet prefix using '/'        64/
        subnet prefix using '-'
        ip range            
        ip start                

    edgedirector servers are compatible with reverse dns PTR records in the zone for ipv4 or the zone for ipv6. Clients who have PTR record requirements will need to contact support to have the zones setup in their accounts prior to use.