How does a DHCP server handle network faults?

In the network structure, we will encounter the use of the DHCP server, and its IP management function is clear to everyone. Here we will explain how to use a DHCP server to handle network faults. A DHCP server is a server that dynamically allocates IP addresses to clients in the LAN. It works in our daily network environment, but is not very valued, most people think that it is only a type of server that can be configured by network administrators. In fact, the clever use of DHCP servers can solve many tricky network faults, the following two examples show the role of the DHCP server in solving network faults.

In the company's actual network environment, there are many small-sized local networks, which are usually located in a large office room with more than a dozen computers, connect with a common switch or HUB, and there will also be a computer that acts as the printer server (that is, this computer is connected to a printer, and other computers are printed by sharing the printer ), 1.

In general, the network management allocates a continuous fixed IP address for the Microcomputer in the small LAN, and then implements the Internet access through NAT on the upper-end router or firewall, however, in a small LAN with only dozens of IP addresses, IP address conflicts often occur. The reason is that someone forgets the IP address of his or her machine and just guesses the IP address, or one day someone brought a laptop from home without an IP address and guessed it. The result is of course an IP address conflict, but it is hard to find a machine with an IP address conflict, the network environment is too bad, so it is not convenient to use network management tools to find conflicting IP addresses, in this case, we can make the printing server into a DHCP server (because the printing server has the longest boot time and can ensure the effective operation of the DHCP service, the network administrator can configure the IP address segment allocated for this small LAN to the IP address range of the DHCP server. For specific operations, I will describe the configuration steps (you must note that, this chapter describes the configuration of the DHCP server, provided that the DHCP server and the client are in the same VLAN )｡

(1) After the DHCP server is enabled in this small LAN, IP address conflicts are basically "Extinct ｡

The DHCP server uses the WIN2003 Operating System (or the WIN2000 operating system). If the DHCP service is not installed, install the DHCP service in "Add/delete programs" on the "control panel,

(2) configure the DHCP server

The configuration process is also very simple. After understanding several concepts (scope, routing, DNS, etc.), you can create a DHCP server. I will take specific operations as an example ｡

1. For example, if the IP segment allocated by the network management system for this lan is 10.66.5.1-10.66.5.100, it is the local machine (DHCP server + Print Server) the assigned IP address is 10.66.5.246 (an IP address assigned by the backend to avoid conflict). The subnet mask is 255.0.0, the gateway is 10.66.0.1, And the DNS server address is 222.175.169.91 and 219.146.0.130 ｡

2. Create a new scope and IP address range

3. Three general settings

Default values are used to add exclusion and Lease Term Options. When "Configure DHCP options" is selected, we select "No, I want to configure these options later ", this aims to eliminate the configuration problems caused by unclear understanding of some terms When configuring the DHCP server for the first time ｡

4. Configure the scope

In this way, we create a scope. In "scope options", right-click and select "configuration options". Here we need to configure two options.

1) 003 Router

Actually, it is the gateway address allocated to the client,

2) 006DNS Server

This is to better understand the IP address assigned to the DNS server of the client.

5. Activate the DHCP server

The DHCP server still cannot work after the scope is created. We need to "Activate" this server, right-click the scope, and select "Activate ｡

IP address Network Test

Test on the client and set the client to automatically obtain the IP address and DNS server address to see if the IP address, gateway address, and DNS server address can be obtained, in the address lease of the DHCP server, you can see that a client has obtained the IP address.

Resolve inexplicable network faults

After a DHCP server is created, some clients automatically obtain the IP address when accessing the internet, and some clients still use the original fixed IP address because their settings have not changed, these two methods can coexist peacefully (because some IP addresses have been excluded, as shown in figure 4 )｡

But one day, one of my colleagues was not on the Internet. I went to his computer and looked at it. It was also a common fault. I could just change the MAC address of his computer to get through, but it will not work again later. This may be because the ARP Address Spoofing virus is playing a role, but the arp-a command cannot be used to identify the specific machine, I want to download the 360 security guard and the arpfirewall software from the Internet, but I am not going to go online at this time. I think there is also a DHCP server in the LAN, so I will set this microcomputer to automatically get the IP address, as a result, the network is successfully connected, and the network is not interrupted ｡

In fact, configuring a DHCP server and running it is not very complicated, but I will usually move the DHCP server on the upper layer of the network down, it can play a role in a small LAN, which can prevent IP address conflicts and solve inexplicable network faults, and assign IP addresses to a small LAN, this DHCP server is not required to have a high configuration. In addition, the DHCP server itself has a much lower probability of problems. This is also a small innovation ｡