(Bosonsim can be regarded as the most popular simulation tool that operates the closest to the real environment. It is no exaggeration to say that it is the epitome of a real device. Compared with the actual experiment, using it eliminates the need for us to make network cables to connect devices, frequently switch CONSOLE cables, and keep going back and forth between devices. At the same time, its commands are also consistent with the latest Cisco IOS, which can simulate Cisco's mid-range 35 series switches and 45 series routers. It also has a very powerful feature, which is to customize the network topology and connections. Through Boson, we can build a network at will, PCs, switches, routers can be simulated, and it can also simulate a variety of connection methods (such as PSTN, ISDN, PPP, etc.). Note that the KeyGen.exe in the compressed package is the registration machine)