I purchased both a Nubus Ethernet card and an Ethernet Transceiver. The transceiver has arrived and is plugged in, AppleTalk worked perfectly first time.
This device plugs straight into the port on the back of the case. Most Macintoshes (if not all) of this era have this port. I imagine they made this obscure port due to the amount of differing network technologies at the time. Nowadays we just have Ethernet, so most devices simply have the same CAT-5/6 port on the machine. Either way, once plugged in, the green link light lit up and the orange even started in tune, following netflix traffic on the network.
MC3NB Rev.B2 Asante Ethernet Card
This card is a relic and reminds me of the good old ISA days with BNC (thinnet networks.) It has an AUI (or AAUI) port for hooking up a transceiver ... although it already has a UTP/RJ45 connector on it, so I just need to plug it in!
Slapping it in the tower was straight forward... I put it in a higher slot than the video card, leaving ventilation room for the PowerPC card.
Once installed, I powered on the machine. As you can see from above, all the existing Ethernet extensions failed. Once on the desktop, the standard "AppleTalk is not working" dialog appeared. First guess is that I need drivers for this device. I jumped on my main PC, visited The Mac Driver Museum: Network and downloaded Asanté Ethertalk Installer Version - 5.2.9 (636k, 800k disk image) as the 5.6.1 is a broken FTP link. I then booted up a2server and copied the hqx into the G2FILES directory. I had to reboot the Quadra with the above Ethernet Transceiver plugged in to get the file across!
The install went well and forced me to reboot. I had forgotten to disable the failing Ethernet extensions so the boot up was slow... they take their time to report a fail. A new icon appeared at the end of the boot extension list for the Asante driver. At the desktop, AppleTalk still failed to start, but this was expected as it didn't know to switch to the new interface. Opening the AppleTalk control panel and selecting "Ethernet Slot 3" worked like a charm.
Testing the Internet, I double-clicked the 'Browse the Internet' icon and IE threw the usual "cannot connect to internet" error. TCP/IP was still trying to use the old Ethernet interface. I therefore went in to the TCP/IP control panel and switched the interface to the newly available "Ethernet Slot 3". Remembering to close and save settings (leaving as DHCP), hitting refresh on apple.com.au got me straight on the net... until IE threw an exception and I landed in MacsBug! To exit the MacsBug debugger (I had no intention on fixing IE), type in es, the abbreviation for 'Exit to Shell'.
I used CockatriceIII as a fileserver. It works with all versions of windows and uses the winpcap library for ethernet. BasiliskII will work if you have something less than Win7-32bit. Both machines saw each other instantly. Even better, I'd had my MacOS 8.1 CD inserted on CockatriceIII and could just share it to the Quadra. I started installing on a blank partition (the machine came with 2 SCSI drives with 4 partitions each... overkill?)
Note that from here I loaded up a2server on the network... following their instructions, the vm came up perfectly in VirtualBox (make sure you select a WIRED ethernet adapter, in bridge mode and promiscuous-mode:ALLOW ALL.) Also note that you should not use the A2FILES share. This has a limitation that all file names need to be upper-case and max 15 chars. I talk more about this in another post.
There's a lot of drivers available at the The Mac Driver Museum: Network. Note that the site also has drivers for just about every other peripheral for a machine of this vintage.
If you need network tools, then visit Old Macintosh System Software and TCP/IP. You'll find all of the basic low-level networking tools to diagnose issues.
There's drivers and tools over at Glenn's ethernet cards and drivers page.
A lot of it relating to the SE/30. Apple Fool has the Classic Mac Networking Guide which will tell you everything you need to get your Macintosh on the Internets.
And finally, the System 7 Help Center provides more network drivers and articles on how to install, configure and work with System 7 in the 21st century.