Network composition analysis of DHCP servers

Complex networks can be controlled without a single protocol. Here we will introduce the DHCP protocol. Next we will look at the use of the DHCP server and DNS server. The scale of modern enterprise networks is getting bigger and bigger. In the face of a large number of clients, it is very troublesome to manually Configure TCP/IP for each machine on the client, therefore, many network administrators use the Windows system's DHCP (Dynamic Host Configuration Protocol) server to dynamically allocate TCP/IP configurations. I'm sure everyone is familiar with the DHCP server, but are you sure you have used it? There may be a lot of practical tips for configuring DHCP servers. You didn't pay attention to them at ordinary times. Let's take a look!

Modify the gateway and DNS Server
 

  　

Figure 1 modify the gateway address

Due to work requirements, some local networks often need to modify the addresses of gateways and DNS servers. In fact, the DHCP server integrates the gateway configuration and DNS server configuration functions, but you only pay attention to its dynamic IP Address Allocation Function and ignore other features. Since the default gateway and DNS server can be configured on the DHCP server, it is very easy to modify the default gateway and DNS server used by the client.

In the DHCP manager window, expand the scope and select "scope options". The vro and DNS server items are displayed in the right box. Double-click "vro" to bring up the "scope options" dialog box (1). Select the original gateway IP address in the default gateway list box and click "delete ", enter the new gateway IP address in the "ip address" column, click "add", and then click "OK" to modify the default gateway. The DNS server is modified in the same way, so we will not repeat it here.

Bound IP address and MAC address

To prevent unauthorized IP address theft, network administrators can use multiple methods to bind IP addresses to MAC addresses. Using a DHCP server is one of them. It also integrates the binding function.

● Find the customer's MAC address

To use a DHCP server to bind an IP address to a MAC address, you must first know the MAC address of the client. On the client side, you can use the "ipconfig/all" command to query MAC addresses.

● Fast binding
 

Figure 2 bind a MAC address

After knowing the MAC address of the client, you can bind the IP address to the MAC address on the DHCP server. Open the DHCP manager, expand the scope used by the client, right-click the "retain" option, and select "New retain". The configuration dialog box is displayed (2 ). Enter a name for the project in the "retain name" column, enter the IP address to be used by the client in the "ip address" column, and enter the MAC address of the client in the "MAC address" column, then, select the "two" option in the "Support Type" box, and click the "add" button to bind the Client IP address to the MAC address.

Cross-subnet DHCP server

To improve network security, a larger LAN is usually divided into multiple subnets. However, the DHCP server can only provide services for the machines in this subnet. configuring the DHCP server for each subnet will result in waste. How can I enable a DHCP server to provide TCP/IP configuration services for multiple subnets at the same time?

Taking the two subnets A and B managed as an example, subnet A is configured with a dhcp server, and subnet B does not have a dhcp server. The following configuration operations are performed on subnet B:

1. Configure routes

In subnet B, select A Windows 2003 machine and configure it as A router to connect two subnets, A and B. Go to "Control Panel> Management Tools", run the "Routing and Remote Access" tool, right-click the local server, and select "configure and enable Routing and Remote Access". The installation wizard dialog box is displayed, select "custom configuration", click "Next", select "LAN routing", and click "finish ".

2. configure a relay proxy

In the Routing and Remote Access Windows, expand "Local Server> IP Route Selection> General", right-click "General", and select "add route protocol ", select "DHCP relay agent" in the new routing protocol window and click "OK.

Right-click the DHCP relay agent and select "properties". The "DHCP relay agent properties" dialog box is displayed, on the "General" tab, enter the IP address of the DHCP server of subnet A in the "server address" column, click "add", and then click "OK.

Right-click the DHCP relay agent and select "New Interface". The dialog box for the new interface of the DHCP relay agent is displayed. In the "interface" box, select the interface that can access subnet, that is, to connect to the NIC of subnet A, click "OK. In the displayed "DHCP relay properties" dialog box, make sure that the "relay DHCP packet" is selected, its relay function is enabled, and then click "OK. After completing the preceding configuration, the client of subnet B can use the DHCP server of subnet.

Tip: the relay proxy is a small program that transfers DHCP/BOOTP messages between DHCP clients and DHCP servers in different subnets. Next we will configure this Windows 2003 Server as a DHCP relay proxy server. In this way, when A client of subnet B sends A request, the relay proxy forwards the request to the DHCP server of subnet, then, the TCP/IP configuration information returned by the DHCP server is forwarded to the client of subnet B.