What's New with Windows Server 2003 DHCP
DHCP is not a new service in Windows Server 2003, but it has undergone some changes from both Windows 2000 and Windows NT 4.0. The following list summarizes some of the major changes in DHCP in Windows Server 2003, as compared to Windows 2000 Server and Windows NT 4.0:
- DHCP integration in DNS—Windows Server 2003 DHCP servers can trigger dynamic updates in the DNS database for all clients to which it leases IP addresses. Windows 2000 and newer clients can automatically update their DNS records if they are authorized to do so. Legacy clients can have their records updated by the DHCP server if it is authorized to do so.
- Rogue DHCP server detection—Unauthorized, or rogue, DHCP servers can cause a wide variety of problems, including denial of service (DoS) to clients. To prevent such problems, Windows Server 2003 provides for authorizing DHCP servers and detecting and shutting down unauthorized servers. Active Directory is required for the detection of rogue DHCP servers to occur.
- Superscope and multicast scope support—Superscopes enable you to group several standard DHCP scopes into a single administrative group without causing any service disruption to network clients. Multicast scopes enable you to lease Class D IP addresses to clients for participation in multicast transmissions, such as streaming video and audio transmissions. Multicast scopes are discussed in more detail in the section "Understanding Multicasting and Multicast Scopes," later in this chapter.
- Local security groups for DHCP management—Two new local administrative security groups are created when the DHCP service is installed: DHCP Users and DHCP Administrators. The DHCP Users group can be used to provide read-only console access to the server to enable group members to view but not modify DHCP data. The DHCP Administrators group provides full administrative control of the DHCP service without granting its members full administrative control over the entire server.
- Improved monitoring and reporting—DHCP is a critical network service that must be kept running. The key to discovering problems early is monitoring, so Windows Server 2003 provides a full set of performance-monitoring counters that can be used to monitor DHCP server performance.
- Custom DHCP option classes—User- and vendor-specified option classes can be used to distribute specific options to the clients that need them. For example, you can use option classes to distribute a specific default gateway or parent domain name to one group of computers on a network.
- In-console backup and restore—For the first time ever, Windows Server 2003 provides the administrator with the capability to perform DHCP scope backups and restorations from within the DHCP console itself.
Now that we've briefly examined the improvements made in the DHCP service in Windows Server 2003, we need to spend some time examining four of the more basic parts of planning for a new DHCP implementation.