DHCP server management knowledge

DHCP servers are a key part of network components. I believe most network administrators are familiar with the management and maintenance skills of DHCP servers. However, in different management and operation environments, we have different management requirements for DHCP servers, which requires us to be good at summing up, only by promptly discovering "tricks" for management and maintenance in the new environment can the DHCP server always run efficiently! This is not the case. The new maintenance skills for DHCP servers summarized below will bring you a fresh feeling!

Cleverly "migrate" the DHCP server"

Hardware upgrades on servers are inevitable. During each upgrade, network administrators often need to spend a lot of time re-configuring the data on the DHCP server and other Parameter options! In fact, there is a skill to "move" the DHCP server. As long as we "move" the DHCP server as follows, we can get twice the result with half the effort:

First, export the DHCP parameters in the old server to a specific text file. When exporting DHCP server parameters, you can click "start"/"run" on the old server system desktop. In the displayed system running dialog box, enter the string command "cmd ", click Enter to switch system status to MS-DOS window status;

At the doscommand line prompt, enter the string command "netsh dhcp server export C: \ dhcpback.txt all" 1) and click Enter, all configuration parameters in the DHCP server will be exported and saved to the "C: \ dhcpback" file, and the plain text file will be copied to the flash drive;

 

Figure 1

Once the preceding string command is successfully executed, right-click the "my computer" icon in the old server system desktop and execute the "manage" command from the shortcut menu that appears, open the Computer Management window of the local server system. In the left-side list area of the window, double-click "services and applications"/"services" projects with the mouse, in the list area on the right of the corresponding "service" project, double-click "DHCP service". In the displayed dialog box, click "stop, temporarily stop the DHCP service in the old server system;

Log on to the new server system as a super administrator, and copy the "dhcpback" file in the flash drive to a specific partition directory of the local system, suppose we still save the file to drive C. Then, click "start"/"run" on the desktop of the new server system. In the displayed dialog box, enter the string command "cmd" and click the Enter key, switch the system status to the MS-DOS window state; then, at the doscommand line prompt, enter the string command "netsh dhcp server import C: \ dhcpback.txt all, after a single return, all the configuration parameters in the dig dhcpback.txt file will be imported to the newly created DHCP server. After completing the preceding operations, run the "Start", "program", and "Administrative Tools" commands in sequence. Then, double-click the "DHCP service" icon in the displayed Management Tools window, in the displayed DHCP server console, right-click the target DHCP server and run the "Start" command in the shortcut menu, in this way, the newly created DHCP server will soon run normally. Of course, the above method is only valid in Windows 2003 Server systems.

If the original DHCP server is built on the Windows 2000 server system, we can use a DHCP parameter import and export tool named Dhcpexim to "migrate" the DHCP server ". When using the Dhcpexim tool to export DHCP server parameters, first download the Dhcpexim tool from the Internet and install the program to the old server system by default; after the Program is installed, open the system Resource manager window, go to the "C: \ Program Files \ Resource Kit" folder window, and double-click the "Dhcpexim" Program, on the settings page that appears, select the "Export configuration of the local service" item and click "OK". Then, a File Save dialog box appears on the System screen, we can specify a file here to save the exported DHCP server parameters. Suppose we specify the "C: \ dhcpback" file to save the DHCP server parameters.

Once the configuration parameters of the old DHCP server are successfully exported to the "C: \ dhcpback" file, the Computer Management window of the old server system is opened. In the left-side list area of the window, double-click "service and application"/"service" projects, and double-click "DHCP service" in the "service" project list area on the right ", in the displayed DHCP service attribute settings window, click "stop" to stop the DHCP service in the old server system. Next, we will install the Dhcpexim tool in the new server system, then, go to the "C: \ Program Files \ Resource Kit" folder window and double-click the "Dhcpexim" Program, on the settings page that appears, select the "Import configuration to the local service" project and click "OK". A file selection dialog box appears on the System screen, select and add the "dhcpback" file so that the Dhcpexim tool will automatically The configuration parameters in the CP server are moved to the new server.

Reserved IP address for DHCP server management

Generally, in order to prevent other users from using IP addresses at will in the LAN, we often use the address binding method to avoid IP addresses being used at will; the common method for binding static IP addresses is to execute the "arp-s ip mac" string command. However, this method cannot be used for reserved IP addresses on DHCP servers, in this case, can we prevent others from using the reserved IP address of the DHCP server at will? In fact, we can easily bind the reserved IP address of the DHCP server to the physical address of the NIC of a specific computer, this prevents others from using the IP address reserved by the DHCP server at will:

First, log on to the system where the DHCP server is located as a super administrator, and execute the "Start"/"run" command on the system desktop to open the "run" text box of the server system, fill in the string command cmd and click OK to switch the system status to the MS-DOS working status;

Then, at the doscommand prompt, enter the string command "Netsh Dhcp Server aaa. aaa. aaa. aaa Scope bbb. bbb. bbb. bbb Add reservedip ccc. ccc. ccc. ccc ddd. ddd. ddd. ddd "username" "Client" "Both" ", where" aaa. aaa. aaa. aaa indicates the IP address of the host where the DHCP server is located, and bbb. bbb. bbb. bbb indicates the IP address of the subnet where the DHCP server is located, "ccc. ccc. ccc. ccc indicates the specific reserved IP address of the DHCP server, "ddd. ddd. ddd. ddd indicates the physical address of the NIC device of the specific workstation. username indicates the specific account name used to connect to the DHCP server. "Client" indicates binding the reserved IP address from the Client, this address binding mode is usually used by default. Therefore, this parameter can be omitted and not written. We only get the dynamic reserved IP address from the DHCP server. After clicking the Enter key, we can bind the reserved IP address to the physical IP address of the NIC of a specific workstation. Once the binding operation is successful, then others cannot use the reserved IP address on the DHCP server at will.

For example, an enterprise has a DHCP server whose Host IP address is 192.168.10.11. Now we want to bind one of the reserved IP addresses "192.168.10.19" to a specific workstation Nic in the LAN, the physical address of the NIC of the specific workstation is "00-16-17-3D-43-EB", and we want to access the DHCP server from the client through the "abc" account. To complete the above address binding operation, run the "Netsh Dhcp Server 192.168.10.11 Scope 192.168.10.0 Add reservedip 192.168.10.19 0016173D43EB" abc "both" "string command at the doscommand line prompt ).

 

Figure 2

DHCP server management across subnets

We know that each scope of the DHCP server can only correspond to one subnet, and common unit subnets can only use up to 253 IP addresses, therefore, a DHCP server can contain up to 253 IP addresses, obviously, the number of available addresses is difficult to meet the application requirements for LAN addresses with large subnets. Can we centralize IP addresses that can be used in multiple subnetworks into one DHCP server so that the same DHCP server can perform cross-subnet services? The answer is yes. We create a super scope in the DHCP server, and then combine all the IP addresses in different subnets to specify that they use the same scope name together, in this way, the DHCP server can serve multiple subnets at the same time. The specific implementation steps are as follows:

When creating a super scope on the DHCP server, we should first create a subdomain for each subnet in the LAN, then, the IP address ranges that can be used in each subnet are correctly imported into the corresponding subdomains. After creating subdomains for each subnet, now we can run the "Start", "program", and "Management Tools" commands in sequence, and then double-click the "DHCP service" icon in the displayed Management Tools window, in the displayed DHCP server console, right-click the target DHCP server and run the "create super scope" command in the shortcut menu. In the displayed dialog box, click "Next". Then, the wizard will automatically prompt you to name the super scope. Suppose we name the super scope "cross-network service ";

After obtaining a proper name for the super scope, click "Next" as prompted to go to the setting page shown in figure 3, on this page, we can see all created subdomain names, select all subscope names, and click "Next" until you finally click "finish, in this way, the DHCP server can provide dynamic IP Address Allocation services for each subnet in the LAN at the same time. Later, when the DHCP server receives an IP address request from any subnet, it will automatically search for available IP addresses under the corresponding subdomain under the super scope, then, assign a correct IP address to the target workstation.

 

Figure 3

Summary:

After the above "tricks", I believe that your DHCP server management can be "Carefree" to a certain extent. However, in the actual application process, there are always ever-changing Problems and Solutions. The above ideas can only be regarded as "throwing a brick and mortar". A lot of practices and a lot of summaries are the right way.