(1. Understand the principle of subnet distinction and the use of variable-length subnet masks, so that computers and devices in the network can be accurately equipped with IP addresses and masks after distinguishing subnets. 2. Master the configuration method of each port on the router in the subnet distinction, including ip address, open port, serial port clock, etc. 3. Understand the principle of the rip protocol and master the commands for configuring the rip protocol on the router. The zip package contains the following files:)