10米的網線太單薄,電源線的電阻太大,5V電源經過10米電線,到達網卡可能已經掉到3V以下了。
方法是找根粗些的電阻小的網線。比如這種:
50 ft feet RJ45 HEAVY DUTY CAT6 UL COPPER Ethernet LAN Network Cable Patch Cord
http://www.ebay.com/itm/50-ft-feet-RJ45-HEAVY-DUTY-CAT6-UL-COPPER-Ethernet-LAN-Network-Cable-Patch-Cord-/161711881558?hash=item25a6c77d56