Dynamic Host Configuration Protocol (DHCP)
Applies To: Windows Server 2008
Dynamic Host Configuration Protocol (DHCP) is an IP standard designed to reduce the complexity of administering address configurations by using a server computer to centrally manage IP addresses and other related configuration details used on your network. The DHCP service enables the server computer to perform as a DHCP server and configure DHCP-enabled client computers on your network.
DHCP includes Multicast Address Dynamic Client Allocation Protocol (MADCAP) which is used to perform multicast address assignment. When registered clients are dynamically assigned IP addresses through MADCAP, they can participate efficiently in the data stream process, such as for real-time video or audio network transmissions.
- When you deploy Dynamic Host Configuration Protocol (DHCP) servers on your network, you can automatically provide client computers and other TCP/IP based network devices with valid IP addresses. You can also provide the additional configuration parameters these clients and devices need, called DHCP options, that allow them to connect to other network resources, such as DNS servers, WINS servers, and routers.
What a DHCP server can provide…
DHCP is a client-server technology that allows DHCP servers to assign, or lease, IP addresses to computers and other devices that are enabled as DHCP clients. With DHCP, you can do the following:
- Lease IP addresses for a specific amount of time to DHCP clients, and then automatically renew the IP addresses when the client requests a renewal.
- Update DHCP client parameters automatically by changing a server or scope option at the DHCP server rather than performing this action individually on all DHCP clients.
- Reserve IP addresses for specific computers or other devices so that they always have the same IP address and also receive the most up-to-date DHCP options.
- Exclude IP addresses or address ranges from distribution by the DHCP server so that these IP addresses and ranges can be used to statically configure servers, routers, and other devices that require static IP addresses.
- Provide DHCP services to many subnets, if all routers between the DHCP server and the subnet for which you want to provide service are configured to forward DHCP messages.
- Configure the DHCP server to perform DNS name registration services for DHCP clients.
- Provide multicast address assignment for IP-based DHCP clients.
Components of a DHCP server…
The primary components of DHCP allow you to deploy a DHCP server and a Multicast Address Dynamic Client Allocation Protocol (MADCAP) server.
MADCAP is supported in IPv4 only. The DHCPv6 server does not support MADCAP.
All computers and other devices on your TCP/IP network must have an IP address in order for the network to function properly. IP addresses can be configured manually at each computer, or you can deploy a DHCP server that automatically assigns IP address leases to all DHCP clients on the network.
Most client operating systems seek an IP address lease by default, so no configuration on the client computer is necessary to implement a DHCP enabled network; the first step is to deploy a DHCP server.
Before your DHCP server can provide IP address leases to clients, however, a range of IP addresses must be defined at the DHCP server. This range, known as a scope, defines a single physical subnet on your network to which DHCP services are offered. So, for example, if you have two subnets, your DHCP server must be connected to each subnet and you must define a scope for each subnet. Scopes also provide the primary way for the server to manage distribution and assignment of IP addresses and any related configuration parameters to clients on the network.
When you deploy DHCP as a MADCAP server, the DHCP server can dynamically assign multicast IP addresses to clients that want to join the group of clients that receive the information sent in the multicast messages.
Multicasting is useful for the point-to-multipoint delivery of information, such as audio or video information, on an internetwork. Multicasting allows one point, such as a media server, to send the information in a single packet to many recipients by using a multicast address.
The advantages of this method are the use of a single packet and no overhead for keeping lists of recipients. Unlike broadcast packets, multicast traffic does not disturb those nodes who are not listening for it. Routers can be multicast-capable and forward the multicast packet to all networks where there is at least one node listening.
Managing a DHCP server:
The primary tools that you use to manage DHCP servers are the Netsh commands for DHCP and the DHCP console.
Netsh commands for DHCP:
You can type the Netsh commands for DHCP in a command prompt window at the netsh dhcp> command prompt, or you can run the Netsh commands for DHCP in batch files and other scripts. All of the functionality that is available in the DHCP console is available at the netsh dhcp>command prompt. This can be useful in the following situations:
- When managing DHCP servers in wide area networks (WANs), commands can be used in interactive mode at the netsh>command prompt to better manage across slow-speed network links.
- When managing a large number of DHCP servers, commands can be used in batch mode to help script and automate recurring administrative tasks that need to be performed for all DHCP servers.
The DHCP console is added to the Administrative Tools folder in Control Panel when you install the DHCP server role. The DHCP console appears as a Microsoft Management Console (MMC) snap-in.
The DHCP console also contains enhancements that were suggested by network managers. These include enhanced server performance monitoring, more predefined DHCP option types, dynamic update support for clients running earlier versions of Windows, and the detection of unauthorized DHCP servers on your network.
Common Administrative Tasks for DHCP:
After you install a DHCP server, you can use the DHCP console or the Netsh commands for DHCP to perform these basic administrative server tasks:
- Create scopes.
- Add and configure superscopes and multicast scopes.
- View and modify properties for scopes, such as setting additional exclusion ranges.
- Activate scopes, multicast scopes, or superscopes.
- Monitor scope leasing activity by reviewing the active leases for each scope.
- Create reservations in scopes as needed for DHCP clients that require a permanent IP address for leased use.
In addition, you can also use the DHCP console or the Netsh commands for DHCP to perform the following optional or advanced setup tasks:
- Add new custom default option types.
- Add and configure any user or vendor-defined option classes.
- Further configure other server properties, such as audit logging or boot protocol (BOOTP) tables.
Superscopes are supported only in IPv4. The DHCPv6 server does not support superscopes.