Simple ideas for network troubleshooting
Check whether the network is normal, generally first make sure the following settings are correct
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First check the physical layer problems, such as whether the network cable is connected correctly
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Check the configuration of the machine, such as whether the ip address and subnet mask are set correctly (ifconfig), whether the default gateway is set correctly (route), and whether the domain name server is set correctly
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Then confirm whether the network card itself can work normally? Use the ping tool to confirm this. Enter ping 127.0.0.1 and see if it can be pinged normally? The 127.0.0.1 here is called the host's loopback interface, which is a prerequisite for the normal operation of the TCP/IP protocol stack. If the ping fails, it can generally be confirmed that there is a problem with the native TCP/IP protocol stack, and the network cannot be connected naturally. However, the probability of this phenomenon is relatively low.
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To confirm whether the network card has a physical or driver failure, use the method of pinging the local IP address. If it can be pinged, the local device and driver are normal.
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To confirm whether you can ping other hosts on the same network segment. This step is mainly to confirm whether the Layer 2 network equipment (such as a switch or HUB) is working properly. If the ping fails, it often indicates that there is a problem on the Layer 2 network, which may involve factors such as switch port working mode, VLAN division, etc.
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To confirm whether you can ping the gateway ip. If the data packet can reach the gateway normally, it means that both the host and the local network are working normally.
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Confirm whether you can ping the iP on the public network. If you can, the local routing settings are correct. Otherwise, you must confirm whether the routing device has the correct nat or routing settings.
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Confirm whether you can ping a domain name on the public network. If it can ping, it means that the DNS settings are correct.
The main situations encountered in the work are mostly ip address conflicts or mac address conflicts. Generally, we still use wireshark to capture packets to check.
By checking whether the mac address responded by the arp packet is the correct device address to detect whether the ip address conflicts; filter the physical mac address to see whether there are different ips to detect whether the mac address conflicts.