GS105v - trying to connect two Apple Macs to my cable modem at the same time

Im only able to connect one Mac computer at a time through the gs105v5 to my cable modem. Connecting both Macs simultaneously won't work. Perhaps I am setting up the network configuration in either Mac (under MacOS operating system) incorrect to work together. Using DHCP. The iMac is connected straight from its ethernet port to the GS105v5 which in turn is connected to my cable modem.

The MacBook is connected via a usb type c hub at:

https://www.amazon.com/gp/product/B06WLHF8BB/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1

which has an ethernet port which then connects to that same netgear gs105v5. The hub mentions a Mac ID but I didn't know whether or where to enter that in that MacBook's network config.

Either connection works if its the only one operating at that moment, but setting up the second connection wipes out the first computer's connection. Under MacOs/system preferences/DIagnostics, the Mac that was disconnected tries to do a self-assigned dhcp, which doesnt work. Fixing one connection wipes out the other. Any instructions how to set them both up in Mac diagnostics to allow each connection to exist? I think I might've even got them both to connect at one point, but the second one's connection had a very slow connection speed and don't recall its config. So just sticking with the original question on setting them up both simultaneously. Any help appreciated.