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 notation.

This method is covered in section of O'Reilly's "DNS & Bind", 3rd Edition.

If you were allocated

  • is the network IP.
  • is the broadcast IP

You would therefore name your zone file:

Your PTR records would look the same as the previous examples:

145 IN PTR

and so on.

In this case we need the hostnames of your nameservers. We delegate the subnet zone to your nameservers using NS records.

Debugging Your Subnet Reverse DNS

If you were allocated (this is a nonworking theoretical example), you would use the following commands to make sure we were pointing reverse to you:

# dig CNAME

Check to see if there is a CNAME record for the IP, using the zone

# dig 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).

 rfc2317.txt (17.33 KB)

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