困擾了好久，今天意外看到這篇
不知道有沒有版友和我一樣買拍賣上面便宜的USB網卡(RD9700)
上Yosemite之後會無法使用，我聯繫過原廠工程師，給我一個driver還是不能用 ~"~
今天無意間看到這篇，直接轉貼上來，已經測試可用
http://blog.inkandfeet.com/How-To-Use-A-Generic-
Usb-20-10100M-Ethernet-Adaptor-Rd9700-On-Mac-Os-1010-Mavericks
Steps to get your adapter working
1. Uninstall the dozens of other drivers you may have installed in the process
of trying to get this working.
2. Unplug your USB adapter, and reboot and give yourself a clean slate.
3. Download and install the drivers from the CD, kindly uploaded by this fine
human being.
4. Reboot.
5. Open your terminal, and run
sudo nvram boot-args="kext-dev-mode=1"
6. Reboot.
7. Open your terminal, and run
"sudo kextload /System/Library/Extensions/USBCDCEthernet.kext"
8. Reboot.
9. Plug in your USB Adapter, with a live ethernet cable.
10. Open System Preferences, and go to the Network Pane.
11. Hit the + button in the bottom right, select the "USB 2.0 10/100M Ethernet Adapter", and hit add.
12. You're all set! Your adapter works!