In this issue, we will share with you basic network troubleshooting knowledge. 1. Problem description During the use of the network, there is a chance that the entire network terminal will be disconnected and unable to access the Internet. Please refer to the following for possible reasons and detailed inspection methods. 2. Possible causes: Problem with the export bandwidth. The export bandwidth is disconnected, causing the entire network terminal to be unable to access the Internet. There is an illegal DHCP server on the network, causing the terminal to obtain an incorrect address and be unable to access the Internet. There is a device on the network that conflicts with the gateway IP, causing a gateway ARP conflict. The terminal learns incorrect ARP information and is unable to access the Internet. There is a problem with the quality of the network export. The export bandwidth is insufficient or the number of connections is insufficient, causing the terminal to be unable to access the Internet during peak hours. There is a loop in the network, causing multicast packet flooding, affecting the use of the entire network terminal. There is a problem with the network line. Some nodes in the network have packet loss.
This causes the terminal to access the Internet abnormally.
3. Troubleshooting steps
1. Check the terminal network parameters
(1) Check whether there is an illegal DHCP server
Check the network parameters of the terminal to see if the IP address, gateway, and DNS obtained are correct. If the address is incorrect, it means there is an illegal DHCP server. Removing the illegal DHCP server can solve the problem. Before finding the illegal DHCP server, you can solve the problem by setting the DHCP snooping of the switch.
(2) Check if there is a gateway IP conflict
Check if the gateway ARP information of the terminal is correct. Windows uses "arp -a" to view the gateway ARP message. If the ARP message is incorrect, it means there is a gateway ARP conflict. Remove the illegal device to connect. Before finding the illegal device, you can solve the problem by setting ARP binding.
2. Check the quality of the network line
(1) Check if there is a loop in the network
Turn on the loop protection function of the switch in the network to check if there is a loop.
(2) Check the quality of the network line
The terminal checks the connectivity of the gateway through the ping test. If there is severe packet loss or delay when pinging the gateway, it indicates that there is an abnormality in the network line. It is necessary to ping the gateway, WAN port, WAN gateway, Baidu, etc. step by step to find the abnormal node and check whether there is a problem with the port negotiation rate being too low.
3. Check the quality of the outbound bandwidth
(1) Check the WAN connection status of the router
You can log in to the router WEB page and use the diagnostic tool to select the WAN port to ping the external network. If it cannot be pinged at all, it means that the bandwidth is abnormal and you need to check the broadband line:
(2) Check the quality of the outbound bandwidth
Log in to the router's WEB page, use the diagnostic tool to select the WAN port to ping the external network to check if there is packet loss or delay. If there is packet loss or delay, it means that the broadband quality is abnormal and you need to contact the operator to solve it.
The operator's broadband has a connection limit, which is easy to reach the connection limit during peak usage, resulting in abnormal Internet access on the entire network terminal. At this time, using the diagnostic tool to ping the external network will result in severe packet loss.
