Ah, ok. I do it a bit easier: Connecting the Laserjet directly with a parallel2ethernet-adapter to LAN (not to router, no USB), which works perfect, by the way.

If your adapter is connected via USB to your router, you may have to config routers USB-Ports for binding them to a static IP (useing them as printerports). This should be configurable in routers webinterface.
I have done similar with a Huawei-Router (connected USB-Printer directly) and it works......