If you haven't installed the appropriate driver software for your Ethernet adapter, do so now. Descriptions to perform this task is beyond the scope of this document.
Open the TCP/IP Control Panel and choose 'User Mode ...' from the Edit menu. Make sure the user mode is set to at least 'Advanced' and click the 'OK' button.
Choose 'Configurations...' from the File menu. Select your 'Default' configuration and click the 'Duplicate...' button. Enter 'IP Masq' (or something to let you know that this is a special configuration) in the 'Duplicate Configuration' dialog, it will probably say something like 'Default copy'. Then click the 'OK' button, and the 'Make Active' button
Select 'Ethernet' from the 'Connect via:' pop-up.
Select the appropriate item from the 'Configure:' pop-up. If you don't know which option to choose, you probably should re-select your 'Default' configuration and quit. I use 'Manually'.
Enter the IP address of your Mac (192.168.0.x, 1 < x < 255) in the 'IP Address:' box.
Enter 255.255.255.0 in the 'Subnet mask:' box.
Enter 192.168.0.1 in the 'Router address:' box.
Enter the IP addresses of your domain name servers in the 'Name server addr.:' box.
Enter the name of your Internet domain (e.g. 'microsoft.com') in the 'Starting domain name' box under 'Implicit Search Path:'.
The following procedures are optional. Incorrect values may cause erratic behavior. If you're not sure, it's probably better to leave them blank, unchecked and/or un-selected. Remove any information from those fields, if necessary. As far as I know, there is no way to use the TCP/IP dialogs to tell the system not to use a previously selected alternate "Hosts" file. If you know, I would be interested.
Check the '802.3' if your network requires 802.3 frame types.
Click the 'Options...' button to make sure that the TCP/IP is active. I use the 'Load only when needed' option. If you continuously run and quit TCP/IP applications without rebooting your machine, you may find that unchecking the 'Load only when needed' option will prevent/reduce the effects on your machine's memory management. With the item unchecked, the TCP/IP protocol stacks are always loaded and available for use. If checked, the TCP/IP stacks are automatically loaded when needed and un-loaded when not. It's the loading and unloading process that can cause your machine's memory to become fragmented.
You may ping the Linux box to test the network connection. If you have the freeware program MacTCP Watcher, click on the 'Ping' button, and enter the address of your Linux box (192.168.0.1) in the dialog box that pops up. (This is only an INTERNAL LAN connection test, you can't ping the outside world yet.) If you don't see "replies" to your PINGs, please verify your network configuration.
You can optionally create a Hosts file in your System Folder so that you can use the hostnames of the machines on your LAN. The file may or may not already exist in your System Folder. If so, it should contain some (commented-out) sample entries which you can modify according to your needs. If not, you can get a copy of the file from a system running MacTCP, or just create your own (it follows a subset of the Unix /etc/hosts file format, described on RFC1035). Once you've created the file, open the TCP/IP control panel, click on the 'Select Hosts File...' button, and open the Hosts file.
Click the close box or choose 'Close' or 'Quit' from the File menu, and then click the 'Save' button to save the changes you have made.
The changes take effect immediately, but rebooting the system won't hurt.