Note that the title is past tense. Don’t buy these dreadful things intentionally!
They’re typically advertised as USB 2.0 10/100 Ethernet dongles. The photo will suggest that there’s a Realtek chip inside. It’s all a lie. They’re actually USB 1.1 and 10mbps half duplex. Speeds top out at under 8mbps (bits, not bytes). Pretty much useless for anything these days.
But let’s say you bought one. Worse yet, you bought one a few years ago, forgot how bad it was and bought another one.
Maybe your old one was hanging off a Raspberry Pi Zero running piCorePlayer and was plenty fast for local streaming even FLAC audio. Of course your other players have better network dongles (even the one that was salvaged from an ancient Tivo that was gathering dust in your part pile but I digress).
So you get the bright idea to salvage this useless dongle you just bought and swap it for one of the better dongles being “wasted” on one of your other players. It frees up the better dongle to use for the current project and the piCorePlayer will be just fine… or so you’d think.
You make the swap and suddenly both piCorePlayers with the dm9601 stop working! Swap back to the good dongle, reboot both, all good. Swap back to the dm9601 and both players go crazy. The music server shows both players winking on and off.
No… it can’t be. Do both dongles, purchased years apart, have the same MAC address? Your router seems to think so. You Google the MAC address (00:e0:4c:53:44:58) and start finding lots of confused and unhappy dm9601 owners. Pretty much all the threads ended in abuse (you idiot, just return it!) and frustration.
Ok. Yeah, that hypothetical sucker was me. Both times. I started searching for a solution and finally found this thread that seemed to reach a workable solution: https://forums.raspberrypi.com/viewtopic.php?t=167249.
I tried using ip (or in piCorePlayer’s case ifconfig) to change the MAC address. It worked but the change was only semi-persistent. It seems to generally survive reboots but unsurprisingly gets reverted on power off.
I then tried adding ifconfig eth0 hw ether "00:11:22:33:44:55"; killall -USR1 udhcpc to various places in the startup script but it wasn’t working consistently. Too early and it wouldn’t take effect. Too late and the player would come up with the default MAC and then change later leaving behind phantom players in the media server.
The working solution was to add the command to the udev rules to change the IP right as the dongle comes up – I didn’t even need to poke udhcpc afterward.
I created a file called 77-mac-fix.rules in /etc/udev/rules.d with the following:
ACTION=="add", SUBSYSTEM=="net", DEVPATH=="/devices/platform/soc/20980000.usb/usb1/1-1/1-1.4/1-1.4:1.0/net/eth0", ATTR{address}=="00:e0:4c:53:44:58", RUN+="/sbin/ifconfig eth0 hw ether 00:11:22:33:44:55"For piCorePlayer I also had to add the file path etc/udev/rules.d/77-mac-fix.rules to /opt/.filetool.lst and run pcp backup to make the change permanent.
A word about that DEVPATH. You’ll need to find one for your specific dongle. Look in /sys/class/net/ to find the path for your dongle:
$ ls -l /sys/class/net/
total 0
lrwxrwxrwx 1 root root 0 May 30 11:45 eth0 -> ../../devices/platform/soc/20980000.usb/usb1/1-1/1-1.4/1-1.4:1.0/net/eth0/
lrwxrwxrwx 1 root root 0 Dec 31 1969 lo -> ../../devices/virtual/net/lo/So for my device (eth0) the DEVPATH was /devices/platform/soc/20980000.usb/usb1/1-1/1-1.4/1-1.4:1.0/net/eth0. My two dongles were slightly different so yours probably will be too.
I hardcoded different MAC addresses for each of my players and now they’re both working as expected.
But really. These things never should have been produced in the first place. Don’t buy one.