It is possible that some non-Apple (third-party) Ethernet NuBus cards installed in a Apple Duo Docking stations will not work with the PowerBook 2300 series computers even if they work with all other PowerBook Duo computers.
In contrast, the Apple Ethernet NB card (M0417LL/B) works with all models of PowerBook Duo computers including the 2300 series. It is possible that some third-party Ethernet board manufacturers may not have followed the Apple design specifications closely enough, resulting in some problems with the 2300 series.
If you have a non-Apple Ethernet card in your Duo Docking station that is not working with a PowerBook 2300 series computer, you should contact the vendor of that NuBus Ethernet board/card for more information concerning compatibility.