Solution: Check whether these pinged computers are installed with a firewall first. The three-layer switch can set the VLAN (virtual local area network). Workstations in different VLANs cannot be pinged without setting the route, so it is necessary to modify the VLAN settings so that they are in a VLAN, or set the route so that VLANs can communicate with each other. This kind of fault is sometimes difficult to detect and requires a certain amount of experience. Before configuring, it is best to read the manual. If you can’t ensure that there is a problem with the user’s configuration, please restore the factory default configuration first, and then configure it step by step.