I recently installed the Routing & Remote Access service on a Windows Server 2008 R2 domain controller. While this is not a recommended approach, it was unfortunately the only server available to host the role. Shortly after installing the role and binding it to the DHCP service, I noticed that when pinging the domain controller it was returning an IP address in the DHCP range. On further inspection it appeared the IP address assigned to the virtual RRAS adapter was registering against DNS and therefore creating two entries for the domain controller. To resolve this issue, the following steps were performed.
1. Navigate to Start -> Administrative Tools and click the DNS option.
2. When the DNS console opens, expand the “Forward Lookup Zones” container and then expand your local domain name.
3. Locate the incorrect host A record for your domain controller and delete it by right clicking the record and selecting delete.
4. In the DNS console, right click the servers name and select properties.
5. In the properties window click the listeners tab and select the “Only the following IP addresses” radio button.
6. In IP addresses list remove the incorrect IP address and then click ok and exit the DNS console.
That’s it, you should no longer experience duplicate DNS entries for your domain controller.