A detailed explanation of IP conflict and resolution of IP and server in switch

Source: Internet
Author: User
Symptom symptom the client in the company's local area network uses the Windows 98 operating system, but one day after the client is turned on: Successfully authenticated when logging on to NT domain, but entering "" in the Navigator address bar, trying to browse the LAN Web Server Web page Require a username and password (we set the Web service to allow anonymous access), and the authentication domain has changed, whether it is to enter a legitimate user password, Superuser password or Web site, the administrator password can not be authenticated. But using the command "ping" can be answered smoothly. The diagnostic process we first initially estimated that the Web server's user access rights have been changed, but after checking, whether anonymous access or Basic authentication, the fault persists, thus excluding this possibility. Then, we look at the server event log, found that there is an information system detected in the network IP address and network hardware address 00:90:04:e2:28:78 conflict, the native interface has been disabled, network operations can be interrupted at any time. This information indicates that there is a conflict between the IP address of a client on the network and the IP address of the server, and that someone has changed the IP address of a client. As a result, the server and switch disconnected, in the local area network, an IP address for the client to execute the command "ping", get a response, that the Internet does have a 1P address and the same device as the server. Now execute the command "Nbtstat-a 192.168.o.1", but get the result of "HostNotFound". Pinq to explain that two devices can communicate through the TCP/IP protocol, because when installing the NIC in Windows98, you must enter the computer name and workgroup name in the network ID, if the device that conflicts with the server IP address is the WINDOWS98 client, The nbtstat command should return the computer name and workgroup name. On this basis, the device that conflicts with the server IP address is not a Windows 98 client. It is thought that the switch can also set the IP address, but since the network, we use the switch's default settings have been working properly, did someone change the IP address of the switch? To prove this idea, we disconnect the redundant cable on the switch, leaving only the Windows98 client with the server and IP address as, the symptom still exists. Disconnect the server, leaving only the IP address Windows 98 client connected to the switch, execute the command: Ping, still get a response, and finally determine the source of the fault in the switch. Originally, in order to manage, configure the parameter convenient, the switch runs a Web service, provides a web interface (wEB interface), we can set the switch parameters through the Navigator, but this Weh server cannot be accessed anonymously. Each device in the network must have a unique IP address: When the switch's IP address is set to, the LAN Web server aborts the service because of an IP address conflict. When we enter "", we are accessing the Web services on the switch. To eliminate this fault, as long as the LAN Web server and switch IP address to avoid duplication, there are two ways to change the IP address of the switch, one is to use the webinterface provided by the switch, in the Windows 98 client's browser address bar, enter the "http:// ", enter the system default username" Admin ", password does not lose, enter the system in the Ipsetup can change the switch IP address, child tightness mask, default route and so on. Alternatively, you can use the HyperTerminal program included in Windows98 to log in to the switch, which has two other ways: (1) Use the signal cable to connect the WINDOWS98 client's serial port directly to the console port of the switch, and select Direct connection to the serial port when creating a new connection ( Baud rate recommended to use 9600); (2) The use of twisted pair (RJ-45 connector) to connect the WINDOWS98 client with the switch, the new connection is selected via TCP/IP (WINSOCK) mode, enter the switch IP address, the default port number is 23. Using the above two methods to establish the connection, using the system default password login can modify the IP address configuration according to the system menu. Excluding experience because of the company's internal LAN Security considerations, the network when the default configuration of the switch did not make any changes, so that people who know our network device model to use the switch's default password can easily modify the IP address of the switch, resulting in a one-time suspension of LAN Web services. Improvement measures: to the switch to set a unique IP address on the network, and the switch to the default login password all modified to prevent such things from happening again.
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