For most customers Comcast as your ISP upon request can setup reverse DNS entry for your Static IP address scope. However, some customers prefers to have more ‘control’ by having the IP Scope delegated to their Name Server so they update reverse DNS entry on their own.
To request an IP Scope Delegation to the customer’s Name Server. Customer has to either contact our Advance technical support team (1-800-741-4141) or send the following information to a moderator at the Comcast Business forum community.
Full Name Account Number Static IP Scope Name Server
Please note to allow 72 business hours to complete this process and the Static IP Scope has to be larger than: /29