The upstream port is connected to a higher-level switch instead of an external network cable. If two or more switches are used, the upstream port is connected to any port of the superior switch (except the upstream port).
When the lower-level switch is connected to the upper-level switch, the port closest to the uplink needs to be emptied, and other ports can be connected to the PC. Some switches don't have uplink ports, so they can connect at will. However, if you want to connect to the superior, you will generally connect the 1 port and the 2 port in Hong Kong.
Extended data:
The uplink port is a common port on the switch, which is used to promote the cascade between two switches.
Each hub or switch connected to other hubs or switches through the ports of the hub (or switch) is still logically a plurality of managed devices. Devices connected through cascaded ports do not require crossover cables. It uses the same channel as the ordinary utp port adjacent to it, so if it uses the uplink port, it cannot use another ordinary port adjacent to it. These two ports are called * * * shared ports and cannot be used at the same time.
Baidu Encyclopedia-Uplink (a port on the switch)