RFC2317 - Classless Reverse DNS Delegation
Posted by Nick Rose, Last modified by Nick Rose on 30 December 2013 07:53 PM
RFC2317 uses a similar looking naming scheme to RFC4183, but an important difference exists. Your zone name starts with the last octet of your network IP address, followed by a hyphen, then the last octet of your broadcast address, then the rest of the usual three-octets.in-addr.arpa notation.
This method is covered in section 184.108.40.206 of O'Reilly's "DNS & Bind", 3rd Edition.
If you were allocated 172.31.15.144/28:
You would therefore name your zone file:
Your PTR records would look the same as the previous examples:
145 IN PTR somename.com.
and so on.
In this case we need the hostnames of your nameservers. We delegate the subnet in-addr.arpa zone to your nameservers using NS records.
Debugging Your Subnet Reverse DNS
If you were allocated 172.31.15.144/28 (this is a nonworking theoretical example), you would use the following commands to make sure we were pointing reverse to you:
# dig 220.127.116.11.in-addr.arpa. @ns1.scalabledns.com. CNAME
Check to see if there is a CNAME record for the IP, using the zone 144-18.104.22.168.in-addr.arpa.
# dig 144-22.214.171.124.in-addr.arpa. @ns1.scalabledns.com. NS
Check the name servers listed.
The first command checks to see what subnet we are pointing an IP in your range to (via a CNAME record) and the second checks where we say the DNS for that subnet is (via a NS record).