Ethernet Network cards communicate using the -addressing: the Ethernet address programmed into the network card by the manufacturer. You can view the Ethernet-address using the configuration program of the Network card (if it has one), like in this example for the 3C509: If you have the installed, you can use ' WINIPCFG' to display the MAC-address (start it via the RUN-menu): The first 6 digits of the Hexadecimal MAC-address indicate the manufacturer (large manufactures have several ID-codes), the last 6 digits are a unique number assigned by the manufacturer for each card. This MAC/Ethernet-address is UNIQUE world-wide! To understand now some of the requirements on setting up and configuring the IPX/SPX network protocol, it helps to understand the history of this protocol: It was developed by for for its PC-based fileserver product called 'Netware'. Multiple network boards can be installed in a Netware server, which is often done to improve network performance. For EACH network-card with its attached network-cable, a -number is assigned on the Netware server (in addition, each Netware server requires an internal NET-number for itself).