If your IP provider does not automatically configure the CNAME record on your behalf, you will need to add a CNAME record for each host at your ISP. This is the final step in the process of setting up a Reverse DNS Classless Address Block (partial range of IP addresses) zone. This is done specifically for Reverse DNS zones to ensure requests are properly routed for resolution.
1. Make a note of the IP address and your desired CNAME for each host in your new reverse DNS zone.
2. Contact your ISP and request that they append a CNAME record for each host in your Dyn Managed DNS zone to your account with them.
3. Test the Reverse DNS path by running:
dig -x <insert any regular forward-formatted IP address from the zone> +trace
The returned information should show that your reverse domain is now being resolved.