If you find that you can not resolve IP’s back to a name on your network check your DNS REVERSE LOOKUP ZONE.
However, the A record is not registering into the forward DNS zone. I don't know if I've missed a setting in DHCP that relates to DNS? With forward DNS, you point the zone to your DNS server by registering that domain name with a registrar.With reverse DNS, your Internet connection provider (ISP) must point (or "sub-delegate") the zone ("....in-addr.arpa") to your DNS server.This is a useful setting to configure for anyone, but it is essential for customers running an outgoing mail server on their Cloud Server.This article shows how to add a reverse DNS record (also known as an RDNS record and a PTR record) to map your server’s IP address to a domain name (for example, 126.96.36.199. Perform the following steps the create a reverse DNS record in the Cloud Control Panel: ©2017 Rackspace US, Inc.