Installing DNS, yes this is the step that required when installing AD DS.
I found the article from Microsoft Tech Flash on how to install and configure DNS on Windows Server 2008 and 2008 R2: http://technet.microsoft.com/en-au/library/cc725925.aspx
The content of that page is:
Installing a Domain Name System (DNS) server involves adding the DNS server role to an existing Windows Server 2008 server. You can also install the DNS server role when you install the Active Directory Domain Services (AD DS) role. This is the preferred method for installing the DNS Server role if you want to integrate your DNS domain namespace with the AD DS domain namespace.
Membership in the Administrators group, or equivalent, is the minimum required to complete this procedure. Review details about using the appropriate accounts and group memberships at http://go.microsoft.com/fwlink/?LinkId=83477.
- Open Server Manager. To open Server Manager, click Start, and then click Server Manager.
- In the results pane, under Roles Summary, click Add roles.
- In the Add Roles Wizard, if the Before You Begin page appears, click Next.
- In the Roles list, click DNS Server, and then click Next.
- Read the information on the DNS Server page, and then click Next.
- On the Confirm Installation Options page, verify that the DNS Server role will be installed, and then click Install.
- We recommend that you configure the computer to use a static IP address. If the DNS server is configured to use DHCP-assigned dynamic addresses, when the DHCP server assigns a new IP address to the DNS server, the DNS clients that are configured to use that DNS server’s previous IP address will not be able to resolve the previous IP address and locate the DNS server.
- After you install a DNS server, you can decide how to administer it and its zones. Although you can use a text editor to make changes to server boot and zone files, this method is not recommended. DNS Manager and the DNS command-line tool, dnscmd, simplify maintenance of these files, and they should be used whenever possible. After you begin using DNS Manager or command-line management of these files, editing them manually is not recommended.
- You can administer DNS zones that are integrated with AD DS only with DNS Manager or the dnscmdcommand-line tool. You cannot administer these zones with a text editor.
- If you uninstall a DNS server that hosts AD DS-integrated zones, these zones are saved or deleted according to their storage type. For all storage types, the zone data is stored on other domain controllers or DNS servers. The zone data is not deleted unless the DNS server that you uninstall is the last DNS server hosting that zone.
- If you uninstall a DNS server that hosts standard DNS zones, the zone files remain in the %systemroot%system32Dns directory, but they are not reloaded if the DNS server is reinstalled. If you create a new zone with the same name as an old zone, the old zone file is replaced with the new zone file.
- When they write DNS server boot and zone data to text files, DNS servers use the Berkeley Internet Name Domain (BIND) file format that is recognized by legacy BIND 4 servers, not the more recent BIND 8 format.