New features for DHCP
Updated: January 21, 2005
Applies To: Windows Server 2003, Windows Server 2003 R2, Windows Server 2003 with SP1, Windows Server 2003 with SP2
New features for DHCP
Microsoft® Windows Server 2003 Dynamic Host Configuration Protocol (DHCP) provides the following new features:
DHCP client alternate configuration
With DHCP client alternate configuration, you can easily move a computer between two or more networks, one configured with static IP addresses and one or more configured with DHCP, without needing to reconfigure network adapter parameters, such as IP address, subnet mask, default gateway, preferred and alternate Domain Name Service (DNS) servers, and Windows Internet Name Service (WINS) servers. For more information, see DHCP client alternate configuration and Use DHCP client alternate configuration.
DHCP database backup and restore
You can back up and restore the DHCP database using the Backup and Restore commands in the DHCP console. For more information about the Backup command, see Backing up the DHCP database and Back up the DHCP database. For more information about the Restore command, see Restoring server data and Restore the DHCP database.
The following features were new for Windows 2000 Server and are also provided with the Windows Server 2003 family:
Local groups for providing limited server and console access to DHCP administrators and users
Two local administrative groups are created when a DHCP server is installed on a server computer: the DHCP Users and DHCP Administrators groups. The DHCP Users group can be used to provide read-only console access to the server. Where used, this group grants members the ability to view, but not modify, server data.
The DHCP Administrators group provides a higher level of administrative access. Members added to this group can fully manage and modify any data at the DHCP server, but are not provided full unlimited administrative access, such as if the local Administrators group were used instead to provide administrative access to the applicable DHCP server. For more information, see DHCP groups.
Automatic assignment of IP addresses
For Windows 98, Windows 2000, Windows XP, and the Windows Server 2003 family, DHCP-enabled clients are automatically assigned a temporary IP configuration if a DHCP server is unavailable to provide a lease when the client starts on a network. For DHCP clients running these versions of Windows, the client tries to contact a DHCP server in the background every five minutes to eventually obtain its valid IP address lease.
Automatic assignment is always transparent to users, who are not prompted if the client fails to obtain a lease from a DHCP server. Addresses are self-assigned from a network address range that is reserved for private TCP/IP usage and not used on the Internet.
Enhanced performance monitoring and server reporting capabilities
DHCP is critical to the success of your network infrastructure. Without working DHCP servers, IP clients can lose some or all of their ability to access or use your network. Because many experienced network administrators realize the importance of closely monitoring DHCP servers, several changes have been made to assist in this area.
Performance monitoring counters are available on computers running Windows 2000 or Windows Server 2003 operating systems to help you monitor DHCP server performance on your network. For more information, see Monitoring DHCP server performance.
Expanded scope support for multicast scopes and superscopes
Microsoft DHCP server supports additional scopes that you can use to streamline your ongoing administration of IP address configurations.
New multicast scopes make it possible for DHCP-enabled clients to lease Class D-type IP addresses (126.96.36.199 to 188.8.131.52) for participation in multicast groups. For more information, see Using multicast scopes.
Superscopes (a late addition to Windows NT® Server 4.0) are useful for creating an administrative grouping of member scopes. Superscopes can be helpful when you want to renumber or expand the IP address space on your network without disturbing currently active scopes. For more information, see Using superscopes.
Support for user-specified and vendor-specified option classes
You can use this feature to separate and distribute appropriate options for clients with similar or special configuration needs.
For example, you might assign all DHCP-enabled clients on the same floor of your building to the same option class. You could use this class (configured with the same DHCP Class ID value) to distribute other options data during the lease process, overriding any scope or global default options. In this way, options appropriate to a set of class-member clients in the same network location (such as a specific default gateway or parent domain name) are applied as class-specific options. For more information, see Using option classes.
Integration of DHCP with DNS
A DHCP server running Windows 2000 or Windows Server 2003 can enable dynamic updates in the DNS namespace for any of its clients that support these updates. Scope clients can then use DNS dynamic update protocol to update their host name-to-address mapping information (which is stored in zones on the DNS server) whenever changes occur to their DHCP-assigned address. For more information, see Using DNS servers with DHCP.
Detection of unauthorized DHCP servers through the use of Active Directory® integration
When a DHCP server is unintentionally started on a network, it can cause a variety of network problems. To prevent this scenario from occurring, Windows 2000 Server and the Windows Server 2003 family provide a method for authorizing a DHCP server as well as a means to detect and shut down unauthorized servers.
When a domain member DHCP server running Windows 2000 or Windows Server 2003 attempts to start on the network, Active Directory is queried, and the IP address of the server is compared to the list of authorized DHCP servers. If a match is found, the server computer is authorized as a DHCP server. If a match is not found, the following occurs:
The server is not authorized in Active Directory.
The server is identified as an unauthorized server.
The server stops leasing IP addresses to DHCP clients.
For more information, see Authorizing DHCP servers.
- The server is not authorized in Active Directory.
Dynamic support for BOOTP clients.
The DHCP service provides additional support for BOOTP clients in large enterprise networks through the addition of dynamic BOOTP.
Dynamic BOOTP is an extension of the BOOTP protocol that permits the DHCP server to configure BOOTP clients without having to use explicit fixed address configuration. This feature provides easier administration of large BOOTP networks by allowing automatic distribution of IP addresses (much the same way that DHCP does) without having to change client side behavior.