10米的网线太单薄,电源线的电阻太大,5V电源经过10米电线,到达网卡可能已经掉到3V以下了。
方法是找根粗些的电阻小的网线。比如这种:
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