80/20 design rules is used to balance the action domain allocation, configure multiple DHCP servers on these addresses to serve the same domain.
Using multiple DHCP servers on the same subnet will provide stronger fault tolerance for DHCP clients it serve. There are two DHCP servers. If a server is not available, another server can replace it and continue to rent new addresses or renew existing clients.
Balancing a single network and address scope between two DHCP servers is to let a DHCP server assign an 80% address, while the remaining 20% is provided by the second server.
The multiple DHCP servers use a superficial domain on each subnet in the local area network environment.
When startup, each DHCP client broadcasts the DHCP Explore Message to the local subnet to try to find the DHCP server. Since the DHCP client uses broadcasts during the initial startup, if multiple DHCP servers are active on the same subnet, you cannot preview which server will respond to the customer's DHCP exploration request.
For example, if the two DHCP servers provide services for the same subnet and its client, you can rent a client on either server. The actual lease assigned to the client can depends on which server first responds to any given client. After that, when the client tries to renew, the client is first selected to obtain the lease, may not be available.
If the renewal failed, the client can then post the renewal of the lease to it after it enters the rebound state. In this state, the client broadcasts on the subnet to locate a valid IP configuration and continue in the network. At this point, different DHCP servers may respond to customer requests. If this happens, the response server may send a DHCP negative confirmation message (DHCPNAK) in your response. This can happen even if you first lease the client's original server can be used online.
To avoid these issues when using multiple DHCP servers on the same subnet, use the same configuration as the new super scope on all servers. The super-scope should include all effective scopes of the subnet as its members' role. To configure a member scope on each server, the address must only be used on one of the DHCP servers used on the subnet. For all other servers on the subnet, the same scope of action is used for the same scope of action as the corresponding scope.
DHCP definition
Dynamic Host Configuration Protocol (DHCP) is a TCP / IP standard that simplifies host IP configuration management. The DHCP standard provides an effective way for the use of DHCP servers: the dynamic allocation of the management IP address and other related configuration information of the DHCP client on the network.
Each computer on the TCP / IP network must have a unique computer name and IP address. IP address (and related subnet mask) identifies the primary computer and its connected subnet. When you move your computer to a different subnet, you must change the IP address. DHCP allows you to assign an IP address for the client's dynamic file from the DHCP server IP address database on your local network:
For TCP / IP-based networks, DHCP reduces the workload and complexity of the administrator involved in the computer.
Windows 2000 Server provides a RFC's DHCP service that can be used to manage IP client configurations and automatically use IP address assignments on the network.
Benefits using DHCP
DHCP provides the following benefits to manage TCP / IP-based networks:
Safety and reliable configuration
DHCP avoids configuration errors caused by manually entered values on each computer. DHCP also helps prevent address conflicts caused by reuse the previously assigned IP address when new computers are configured on the network.
Reduce configuration management
Using the DHCP server can greatly reduce the time used to configure and reconfigure the online computer. You can configure a server to provide all the scope of other configuration values when assigning an address lease. These values are assigned using the DHCP option.
In addition, the DHCP lease renewal process also helps ensure that client configuration requires frequent updates (such as users who use mobile or portable computer frequently changed location), communicate directly with DHCP server through clients to automatically perform these modifications. DHCP works
DHCP uses the client / server model. Network administrators create one or more DHCP servers that maintain TCP / IP configuration information and provide them to clients. The server database contains the following information:
Effective configuration parameters of all clients on the network.
The valid IP address maintained in the address pool assigned to the client, and the retention address for manual assignment.
The lease duration provided by the server. The lease defines the length of time that the assigned IP address can be used.
Enable DHCP-enabled clients can dynamically obtain their IP addresses and related configuration parameters each time the DHCP is enabled. The DHCP server provides the configuration to a requesting client in the form of an address lease.
The unauthorized DHCP server is detected by using Active Directory integration.
When the DHCP server is unexpected on the network, it may interfere with the normal TCP / IP network operation. Because the DHCP client frequently uses the broadcast to the network to discover the DHCP server at startup. In order to avoid accidental problems, Windows 2000 Server provides methods of authorizing the DHCP server and how to detect and close unauthorized servers.
When the Windows 2000 DHCP server attempts to start on the network, the Active Directory is queried, and the IP address of the server computer is compared to the list of authorized DHCP servers. If you find a match, the server computer is authorized to be a DHCP server. If no match is found, the server is not authorized and the server is identified as an unauthorized server. In this case, the service of the DHCP server that has been installed and running on the unauthorized server is automatically turned off before the network may interfere.
For these features to use, you must also configure and use the Active Directory with the Windows 2000 DHCP server. Other DHCP servers do not support this feature. Server detection is performed by using DHCP server objects created in Active Directory. This object lists the IP address of the server that is authorized to provide a DHCP service for the client on the network.
DHCP server
Configuring the DHCP server for the network has the following advantages:
Administrators can focus on and designate global and subnet-specific TCP / IP parameters for use by the entire network.
The client does not need to manually configure TCP / IP.
When the client moves between the subnets, the old IP address will be released to reuse. When the computer restarts its new location, the client automatically reconfigure its TCP / IP settings.
Most routers can forward DHCP and BOOTP configuration requests, so the DHCP server is not required on each subnet in the network.
How do clients use servers?
If "Get IP Address" is selected in the "TCP / IP" property, the computer running Windows 2000 becomes a DHCP client. When you set up a client to use DHCP, it accepts lease and can receive the following:
The temporary use of the IP address is valid for the network it is incorporated.
Other TCP / IP configuration parameters used by the client in the form of option data.
At the same time, if conflict detection settings are configured, the DHCP server will try the connectivity of each available address in the PING test domain before providing the address in the lease to the client. This ensures that each IP address provided to the customer is not used with another non-DHCP computer configured with manual TCP / IP.
How to provide optional data
In addition to IP addresses, DHCP servers can configure, providing optional data to fully configure TCP / IP of the client. Some of the most universal DHCP options that are configured and assigned by DHCP servers include:
The default gateway (router) is used to connect a network segment to another network segment. Additional optional configuration parameters assigned to the DHCP client, such as the client can be used to identify the network host name DNS server or the WINS client's IP address.
