Lan Fault Caused by careless network connection Error

The local area network of this unit has been built for several years, and more than 70 computers have been connected to office buildings on the fifth floor. Network topology. Client computers are connected to the network center Switch_w1 through switches or hubs on each floor, and the Internet is accessed through firewalls and routers. The server is connected to the Switch_w2 switch. The firewall has three NICs, one connected to the router and one connected to Switch_w1. The assigned IP address is 192.168.1.1, which is the internal gateway. All the internal user IP addresses are configured to use the 192.168.1.0 network segment; one block is connected to Switch_w2, the IP address is set to 202.106.22.10, the server web, DNS, MAIL, etc.) to access this CIDR block, and a valid IP address is assigned. Computers in the LAN access each other through the firewall and access the internet.

With the constant demand for information access, the number of connected users is also increasing, and the number of ports is also expanding. Recently, it was found that all computers in the LAN 192.168.1.0 segment can access and share resources with each other, but they cannot access the Web servers in the other segment or the Internet, when the gateway is pinged to 192.168.1.1, the packet loss rate is generally over 50%. Another CIDR Block computer can access the Internet, but cannot Ping 192.168.1.1.

Initially, it was thought that there was a problem with the firewall configuration. Go to the firewall management interface to check whether the firewall is correct and then exit and restart. The fault persists. I wonder if the port connecting to the firewall on Switch_w1 is faulty, and the restart problem still exists. When the firewall is disconnected, it is found that it can still Ping 192.168.1.1, which is consistent with the previous fault display. Therefore, it is determined that the problem should not be found on the firewall, but within the network segment 192.168.1.0, suspected that a computer has stolen or used the IP address of the Internal Gateway by mistake. Due to the limited conditions, no suitable network testing equipment or good monitoring software is available to identify the faulty node. Therefore, the faulty network segment is located one by one on the switch. The fault disappears when you unplug the crystal head connected to the Switch on the fourth floor. In this way, we will lock the fault on the fourth floor.

The network settings of all the computers on the fourth floor are carefully checked. If the IP address settings are correct, the problem should be found on the switch on the fourth floor. We expanded the port about a week ago, added a 16-port 100 M Switch, and connected the original two eight-port hubs to the Switch through a twisted pair to increase the number of users. Hub41 is connected to swit44. due to a fault in the Hub42 cascade port, switch4is connected by Jumper. After the device is replaced, users on the fourth floor report that they can access the Web and other users in the network. However, this fault has concentrated the problem on the switch, so I checked the connection again, but found that Hub41 was connected through the cascade interface using jumpers due to staff errors, the Hub42, which has a problem with the cascade interface, is connected to the downstream interface! Switch the two network cables and connect them to the network center Switch. The fault disappears. All computers in the LAN can access the Web server and the Internet normally.

Through troubleshooting this time, we realized that we should strengthen the management of our staff and the requirement for proficiency in their skills, so as to avoid the occurrence of such errors again at work.

• · Use network adapter to solve typical LAN faults