Switch for two ethernet cables (twisted pair)?

Question

Iron

There is a GPON modem with two ethernet ports, one goes to the computer, the second is also used. The same GPON is sometimes used as a router to connect an external drive via eth to a computer. To do this, you have to manually pull out the second cable from the GPON and connect the eth cable from the external drive to it.
Question: are there eth switches in nature so that you can plug this switch into the second port, and have two switched eth ports at the output of this switch (by button, for example)?

Answer 1

instead of a switch, you can make a "hub on resistors".
If you do not need three-way communication, then you can make a splitter (it is simpler): that is, the transmitting pair of port 1 to the receiving pairs of ports 2 and 3 and vice versa.
the connection will be 1-2 and 1-3, there will be no connection between 2-3