If there is something wrong with the cat settings, it can be judged that as long as three machines can surf the Internet at the same time, there should be no problem with the cat settings. (rule out your frequent disconnection first. ) I wonder if there is any problem with those two machines appearing at the same time. If there is no problem, then the cat setting should be no problem. Let's talk about what Hu Gaofei said. I have adjusted the broadband for my customers several times, and I have indeed encountered similar problems. With the solution of cat plus switch with routing, several computers can sometimes access this and sometimes that. If you add a router to an ordinary cat, this problem will not exist, because sometimes ISP will make some restrictions, such as MAC address binding. Because the router has the function of MAC address cloning, cats basically don't, so this possibility is not ruled out. I suggest you try to add a route if you can, and pay attention to the fact that if you add a route, it is best to turn off the cat's routing function to avoid conflicts, especially if the IP address of the route is the same as that of the cat.