AFAIK, the concept of the "default" printer is not a function of the router or USB. It's a function of the client OS (e.g., Windows or Linux).
By default, the first USB printer is assigned port 9100. All subsequent printers get assigned sequentially from there (9101, 9102, etc.). But the problem is that you can't control which USB port gets assigned to which USB printer, and in which order. So the choice of network port assignment (910x) becomes arbitrary. Even if both printers are ON at the time the process begins, there's still no guarantee which printer gets which port. And when that happens, *then* your references to those ports in the client's OS seem to change the default printer.
Joined: 08 May 2018 Posts: 7182 Location: Texas, USA
Posted: Fri Jul 17, 2020 17:29 Post subject:
Right. By default, the first one will be lp0, the additional ones via startup would be lp1, etc. A single printer instance is (now) working again, it's the 2nd printer that goes awry. I found the thread I was thinking about, as I was engaged in the discussion, finally: