The following describes the information that Microsoft Small Business Server customers need to make up a local Domain Name System (DNS) namespace. Microsoft Small Business Server 2000 and Microsoft Windows Small Business Server 2003 install the DNS server and integrate DNS into Active Directory directory service by default during the Setup program. The best practices to set up a Small Business Server network must include both DNS name and Internet Protocol (IP) address considerations for the network. For IP addressing considerations, refer to Request For Comments (RFC) 1918 "Address Allocation for Private Internets." This RFC describes the address ranges for private networks that are used in a Small Business Server environment. For more information about RFCs, refer to the following Web site:

http://www.rfc-editor.org

In addition to RFCs, you can refer to Best Current Practices. Best Current Practices 0005 discusses the best practices to configure IP addressing on a private network. During a new installation of Small Business Server 2000 or Windows Small Business Server 2003, the default IP address range of 192.168.16.0/24 conforms with the recommendations of RFC 1918.

Although the DNS is defined by RFCs, domain naming for private networks is not defined in the manner that IP addressing is defined. During Setup of Small Business Server, the user is prompted to enter the fully qualified domain name (FQDN) of the Small Business Server domain. At this point during Setup, Small Business Server requires the following:

• A local FQDN that Microsoft Windows 2000 DNS or Microsoft Windows Server 2003 DNS can use for local name resolution on the private Small Business Server network.
• A network basic input/output system (NetBIOS) domain name for compatibility with NetBIOS-based programs and client computers.

Three practical methods to name the DNS domain are:

• Make the name a private domain name that is used for name resolution on the internal Small Business Server network. This name is usually configured with the first-level domain of .local. At the present time, the .local domain name is not registered on the Internet.
• Make the name a sub-domain of a publicly registered domain name. For example, if the publicly registered domain name is Contoso.com, a sub-domain of Corp.contoso.com can be used.
• Make the name the same as a publicly registered domain name.

• The management of the local namespace is controlled by the Small Business Server. When you use a private FQDN for local DNS name resolution, the DNS server becomes the start of authority for the local domain. This result means that a query to external DNS root servers is not required for local resource name resolution.
• The security may be increased for your DNS server by not enabling zone transfers by means of the zone transfer properties of the forward lookup zone. Because dynamic registration of internal hosts can occur with the DNS server, if you disable the zone transfers from external clients, you can limit the exposure of internal host names to the Internet.
• The natural separation of internal and external networks occurs because of the use of a separate internal namespace. A client query generated from the Internet for www.contoso.local does not return any valid domain information because .local, at the present time, is not a registered domain name.

The disadvantages of using the sub-domain of a publicly registered domain name or a publicly registered domain name include, but may not be limited to, the following issues:

• Internal clients may be able to resolve resources on the internal domain, however, queries to external resources of the domain are not resolved by the DNS server. For example, if the internal network namespace is configured by using the publicly registered domain name of Contoso.com, only resources that have "A" (Host) records in the forward lookup zone for Contoso.com are available to local clients.
  This behaviour can pose a problem if Contoso.com hosts resources, such as, a web server by means of an external provider or Internet service provider (ISP). Any queries from internal clients to www.contoso.com are resolved as a negative query by the local DNS server because the "A" record for "www" does not exist in the forward lookup zone for Contoso.com. For clients to access external resources, "A" records must be added to the forward lookup zone of the DNS server for those resources.
• The use of a publicly registered sub-domain name can pose the same problems as described for a publicly registered domain name. If at any time, the start of authority for the registered domain (Contoso.com, in this example) adds records for sub-domains, the currently configured private sub-domain may become public. Name resolution problems that are created by using a publicly registered domain name can be avoided by planning the private namespace around a local first-level domain so that, in this example, Contoso.com and Contoso.local are both available to internal clients, but Contoso.com is only available to external internet clients.
• The use of a separate and private DNS namespace for Small Business Server is consistent with the recommendations in the following Microsoft Knowledge Base article: 254680 DNS Namespace Planning

1. Microsoft Windows Small Business Server 2000
2. Microsoft Windows Small Business Server 2003 Premium Edition
3. Microsoft Windows Small Business Server 2003 Standard Edition
4. Microsoft BackOffice Small Business Server 2000 Service Pack 1