If the network user does not set the IP address according to the regulations, the IP address conflict phenomenon is inevitable. Once this phenomenon occurs frequently, it will not only affect the surfing efficiency of the Internet users, but also will not be conducive to the stable operation of the LAN network. In order to improve the stability of LAN operation, we can't wait until the IP address conflict occurs. Then we should take measures and take the initiative to prevent Internet users from rushing to use other IP addresses in the LAN. For this reason, this article starts from the actual point of view. , By setting up the switch cleverly, to control IP address conflict trouble recurring!
Network conditions
For example, there are about 150 network nodes on the LAN. These network nodes are evenly distributed on six floors. The network nodes in each floor are protected by 100M twisted pairs and ordinary Layer 2 switches. Each ordinary Layer 2 switch passes The 1000M optical fiber cable is connected to the routing switch. In order to ensure network access security, all network nodes communicate with the Internet through hardware firewalls.
Currently, the unit LAN uses the IP address of the 10.168.163.0 network segment. The default gateway address used in this network segment is 10.168.163.1 and the subnet mask address is 255.255.255.0. This network segment can have a maximum of 250 In the IP address, only 150 addresses are actually used in the usual work. Obviously, the address space margin is sufficiently large to meet the increasing number of workstations.
However, because the local area network adopts the static address allocation method, whenever the workstation system suddenly crashes or encounters a virus attack and cannot start normally, the users on the Internet are free to reinstall the system and modify the Internet address. As a result, frequent IP address conflicts occur in the LAN. This not only seriously affected the normal Internet access of others, but also increased the maintenance workload of network administrators.
In order to effectively prevent Internet users from arbitrarily changing IP addresses, the author intends to use an address binding method to bind the workstation's IP address with the physical address of the corresponding network card device. However, this method has not yet been officially implemented, and it has been Against the objections of colleagues of network administrators, he believes that this method of palliatives does not solve the problem, because Internet users can still use the method of modifying the physical address of the network card to steal the IP address of others. This is obviously not the most effective solution.
Response plan
After accessing related materials and in-depth analysis on the Internet, the author and another network administrator decided to bind the IP address of the ordinary workstation to the physical address of the network card on the core switch. However, the binding operation can be performed simply and the Internet access cannot be resolved. The user sets the IP address at will, because once an IP address is set and bound, although the Internet user cannot continue to use this IP address, he can still use the idle IP address in the LAN, and thus the IP address. Conflicts may still occur. This is also a problem that many network administrators cannot understand: After binding the IP addresses used by all workstations to the corresponding network card devices in the core switch, address conflict failures cannot be effectively avoided.
To completely resolve IP address conflict failures, we not only need to bind the assigned IP addresses in the LAN to the corresponding network card devices, but also need to bind those IP addresses that are in idle state so that the Internet users can both You can't use the IP address of the connected network workstation, and you can't use the idle IP address of the LAN. So, as long as the Internet users in the LAN can change the IP address at will, he cannot access the LAN network normally. However, after this configuration, it also brings another trouble, that is, if there are new users in the LAN that need to access the Internet, they can not choose their own IP address, but must apply to the network administrator to apply for Internet access in advance. After receiving the application, the administrator needs to log in to the switch back-end management system to assign a free address to the Internet, so that the Internet user can connect to the LAN normally. Practice has proved that this method can not only effectively avoid the IP address conflict failure occurred, but also can effectively prevent the network virus illegally spread through the LAN, which can effectively guarantee the stable operation of the LAN!
Implementation process
According to the above theoretical analysis, the author intends to first bind the default gateway address 10.168.163.1 in the LAN to the corresponding physical address, which can effectively control the outbreak of ARP virus in the LAN; and then think of ways to bind the IP address of the workstation that has been online. Set the operation, and finally bind those IP addresses that are in the idle state to a virtual network card physical address, so that one stone and two birds can be achieved.
When binding the gateway address, the author first logged in as the system administrator into the routing switch background management system, and executed the string command “system†in the command line state of the system to switch the system to the global status of the switch configuration; In the configuration state, enter the string command "arp 10.168.163.1 0215.9cae.1156 arpa". After you click Enter, the default gateway address 10.168.163.1 is successfully bound to the 0215.9cae.1156 MAC address. Other workstations If you grab the 10.168.163.1 address when you surf the Internet, there will be a failure to access the Internet, so that the stability of the entire LAN can be guaranteed.
In order to prevent users from rushing to use other IP addresses, we need to bind about 150 network node addresses that have been connected to the Internet. Because there are a large number of addresses to be bound, we simply rely on manual methods to obtain the physical address and IP address of each network card on the workstation. The workload will be huge. For this reason, the author executes the "display arp" string command in the global configuration state of the switch background system, and then copies and copies the contents of the displayed switch ARP table to the local chronicle editor window. After a simple edit, the content of the modified ARP table is copied and pasted into the switch ARP table. In this way, the binding task of the workstation address that has been accessed online can be quickly completed.
For the remaining 100 or so idle IP addresses, we can manually bind each free IP address to a virtual MAC address, for example, when binding 10.168.163.156 to 071e.33ea.8975. We can execute the string command "arp 10.168.163.156 071e.33ea.8975 arpa" in the global configuration state of the switch background system, and then we bind the other free IP addresses to the virtual MAC address 071e in the same way. 33ea.8975 on.
After the above address binding task is completed, any user cannot change the IP address freely; if a new user needs to use the free 10.168.163.156 address to access the Internet at this time, the network administrator can follow the following steps to convert 10.168. 163.156 addresses are released from the binding address list:
First, execute the “system†command in the background management system of the routing switcher to switch the system state to the global configuration state. In this state, enter the string command “display arpâ€, and then click Enter to enter the ARP list Check if the 10.168.163.156 address is idle. If the destination IP address is idle, we can proceed with the following release steps:
Next, enter the string command "no arp 10.168.163.156 071e.33ea.8975 arpa". After you click the Enter key, the target IP address 10.168.163.156 is released from the address binding list.
The following address 10.168.163.156 to the need to access the user, let him set the IP address to the corresponding workstation system, so that new users can successfully access to the unit LAN network;
Afterwards, in the background management system of the core switch, the string command “display arp in 10.168.163.156†is continuously executed. From the subsequent result interface, we can see that the physical address of the network card corresponding to the address of 10.168.163.156 is 00bb.ebc3.c6d0. ;
After the MAC address is obtained, we can continue to execute the string command “arp 10.168.163.156 00bb.ebc3.c6d0 arpaâ€, so that the IP address of the new Internet user and the physical address of the network card are successfully bound together; Run the string commands "quit" and "save" to save the configuration to the switch system and complete the switch configuration task.
to sum up
Through the above configuration, all IP addresses in the LAN are successfully controlled. Any user who personally changes the IP address will not be able to access the network. Although the entire control process is somewhat complicated, it can control access security of the network. Workstations that do not understand the truth bring network viruses or Trojans into the LAN work environment. Of course, the above control scheme is not guaranteed to be foolproof. There is also a situation where address conflicts occur. That is, an illegal user steals the contents of the switch ARP list. He only needs to modify the physical address and IP address of the network adapter of his workstation. If the stolen user is not online, he can successfully use another person's address to access the Internet. However, this situation is very unlikely, unless the network administrator intends to do so.
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