So, what do you need to get Arcnet running?

• two adapter cards - here I'm assuming you have the most common type: ISA bus, coaxial cabling, STAR topology
• one cable - officially the 93-Ohm RG-62A/U, but for a short distance the 75-Ohm TV coax should be good enough
• two computers with matching slots - Arcnet cards don't use ISA DMA, thus they may work even with those modernish ISA-like things that lack DMA
• compatible software

Almost all Arcnet cards for ISA are based on COM90xx series chips (or compatible), therefore one driver fits all.
They even have the same factory settings:

• I/O 2E0..2EF (16 ports) - conflicts with COM4 at 2E8
• MEM D0000..D1FFF (8 KB) - be careful if you're using the UMB area for anything else
• MEM D2000..D3FFF (8 KB) - only if there's a BOOT ROM installed
• IRQ 2 (equals IRQ 9) - set IRQ 9 to "Legacy ISA" in BIOS where applicable

It's important to correctly set the NODE ID DIP-switches:

• can't be 00000000
• can't be 11111111
• must be unique for each of the stations

There's plenty of software with Arcnet support...

For a quick start, you can use Windows 9x - it comes with the necessary drivers, "Add New Hardware" can find the adapter, just be careful to select correct IO/MEM/IRQ if something gets misdetected.
And then it just works - you can eg. normally share the files.

You can also share files between Win9x and DOS with Microsoft Network Client 3.0.

Arcnet drivers shipped with Windows 9x are NDIS 2.0 (Real mode), and can be used with the three common protocols:
- IPX/SPX
- NetBEUI
- TCP/IP, using "Ethernet-encap"

It may be preferred to use ODI driver instead, which works with:
- IPX/SPX
- TCP/IP, using RFC1201

I'm attaching the ODI driver - load LSL.COM and SMCARCWS.COM from AUTOEXEC.BAT, and then add "Existing ODI Driver".
I'm also attaching an Arcnet BOOT ROM - but that's only because I want to have a backup in case the EPROM evaporates 🤣

Now, some benchmarks...

Server:
- Pentium III 800EB
- ISA 16-bit Arcnet card
- Windows 98 SE

Client:
- Celeron 266
- ISA 8-bit Arcnet card
- Windows 98 SE

SMB copy a file from the server's HDD to the client's NUL.
All results in KB/s.

NDIS + IPX/SPX: 132
NDIS + NetBEUI: 150
NDIS + TCP/IP: 116
ODI + IPX/SPX: 129
ODI + NetBEUI: doesn't work
ODI + TCP/IP: 192

In theory, Arcnet is 2.5 Mbps = 312 KB/s; actual measured performance isn't as close to the theoretical limit as with the Ethernet.
I guess it's due to shorter frames, and with NDIS+TCP/IP there's the additional overhead of "Ethernet-encap" - with both Arcnet header and Ethernet header transmitted, there's less room for payload.

Now, let's connect from Arcnet LAN to modern computers...

Arcnet adapters for modern buses - PCI, PCIe, USB - do exist, but they are niche and expensive.
So I decided to build an Arcnet<->Ethernet router, using a Pentium III machine with Linux.

There are three methods for transmitting IP traffic over Arcnet networks, incompatible with each other:

• RFC1201 - the final standard, probably the best
• RFC1051
• Ethernet-encap

Various software supports various methods:

• Linux 2.3.35 and below (Arcnet driver 3.02 and below): RFC1201, RFC1051, Ethernet-encap
• Linux 2.3.36 and above (Arcnet driver 3.91 BETA and above): RFC1201, RFC1051
• Microsoft Network Client 3.0 for MS-DOS: Ethernet-encap
• PD apps using ARCETHER, ARCPSF, SMCARCWS+ODIPKT: RFC1201
• PD apps using SMC_ARC+DIS_PKT: Ethernet-encap
• Windows 9x using own drivers: Ethernet-encap
• Windows 9x using ODI drivers: RFC1201

So, the best system for the router seems to be Linux 2.2 - I will try it sometime.

As of yet, I've only tested Red Hat 7.3 (based on kernel 2.4.18-3) - here's the procedure for this distro...

Install the package "kernel-source-2.4.18-3.i386.rpm", copy the source from /usr/src to your home directory, and then:

make menuconfig
- Load an Alternate Configuration File: /boot/config-2.4.18-3
- Network device support -> ARCnet devices -> set everything as module:

- Exit, save

make dep
make bzImage
make modules
su
make modules_install
make install

Reboot to the custom kernel, and then you can use the following script:

1insmod arcnet
2# insmod arc-rawmode
3# insmod rfc1051
4insmod rfc1201
5insmod com90xx
6ifconfig arc0 192.168.1.4 netmask 255.255.255.0
7echo "1" > /proc/sys/net/ipv4/ip_forward
8service dhcpd start

ifconfig should display something like:

1arc0      Link encap:ARCnet  HWaddr 01  
2          inet addr:192.168.1.4  Bcast:192.168.1.255  Mask:255.255.255.0
3          UP BROADCAST RUNNING  MTU:1500  Metric:1
4          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
5          TX packets:0 errors:0 dropped:0 overruns:0 carrier:357
6          collisions:0 txqueuelen:30 
7          RX bytes:0 (0.0 b)  TX bytes:0 (0.0 b)
8          Interrupt:9 Base address:0x300 Memory:d0000-d07ff 

Note that I've disabled modules "arc-rawmode" and "rfc1051" - that's because they decrease the MTU to 508 and 507 bytes, which reduces performance.
Only enable them if really necessary!

Hint: to access a Samba server by name across a router, you can enter its IP to the DHCP server config, eg.:
option netbios-name-servers 192.168.169.170;

Excellent writeup but how do you plan to entice people to trying it with zero pics of the hardware?

maxtherabbit wrote on Today, 13:29:

Excellent writeup but how do you plan to entice people to trying it with zero pics of the hardware?

Oh, there's plenty of pictures online - I'm sure everybody interested can easily find them.
I'm not trying to provide everything, only some practical info that I haven't seen online, and had to figure it out experimentally.