I’ve got a 2010 MacBookAir3,1 — 1.6GHz Core 2 Duo — OS 10.6.8

I’ve had a terrible time getting my USB Ethernet adapter to work. Trouble both at home and at the office. Across 3 different adapters.

I’d get either of these messages:

“Self-assigned IP address”

or

“Ethernet is not connected”

After a couple of months of giving up entirely, I’ve done some research and have found a fix of sorts. Steps I took:

1. In System Preferences > Networking …
2. Created a new location, getting off the Automatic location
3. Clicked the plus in the bottom left to create a USB Ethernet connection
4. Under that connection, clicked the “Advanced …” button in the lower right
5. Selected the Ethernet tab (farthest on the right)
6. Edited the settings under that tab as follows:
• Configure: changed from Automatically to Manually
• Speed: 10baseT/UTP
• Duplex: half-duplex
• MTU: Standard

I’ll admit I don’t know what these settings do.

But suddenly my USB is recognized and works.

Though none supplied this fix, I gleaned ideas from these comments in Apple support pages, some of which led me in this direction.

Seems utterly strange to me that there are no published fixes rolled into Apple updates.