This could simply be the difference between running what Apple eventually named "Classic Networking" and "Open Transport Networking"
When Open Transport is running, you use TCP/IP, and AppleTalk control panels. When Classic Networking is running you use Network and (if installed) MacTCP control panels.
If you're running system 7.1 to 7.5.5 run Open Transport 1.1.2 (it's not the most stable thing but should be vastly better than Classic Networking).
A tip; once both are installed, you can switch from one to the other (requires a reboot) and each hides the other's group of control panels from finder view.
The last Classic Networking installer for system 7.x.x is v1.5.1 and can be downloaded from Apple
here
Open Transport v1.1.2 can be installed on 7.1 thru 7.5.5 and is also available
here
If I recall correctly, 7.6 or later can only run Open Transport and is included as part of the system.
EDIT: Also, once you're running Open Transport, each of the control panels (AppleTalk and TCP/IP) should show a new "connect via" option, which will be your card in "slot B1" or something similar - only if the Apple supplied drivers work with the card. If you don't see that option, then you'll need to provide more info on the card itself to find drivers for it.
EDIT 2: the other alternative if locating drivers for your card proves impossible, is to check ebay for "AAUI" to "RJ-45" adapters. They're a bit pricey, but will work with the built-in AAUI connector on the 7100's motherboard.