ping 114.114.114.114 都是ping不通，提示如下：
root@DayDream:/# ping www.baidu.com
ping: bad address 'www.baidu.com'
root@DayDream:/# ping 114.114.114.114
PING 114.114.114.114 (114.114.114.114): 56 data bytes
ping: sendto: Network is unreachable
輸入 route 。發現沒有設置網關：
root@DayDream:/# route
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
113.115.0.1 * 255.255.255.255 UH 0 0 0 3g-ppp0
192.168.20.0 * 255.255.255.0 U 0 0 0 br-lan
於是，設置上默認網關
route add default gw 113.115.0.1
在嘗試一次。發現成功了：
root@DayDream:/# ping www.baidu.com
PING www.baidu.com (180.97.33.107): 56 data bytes
64 bytes from 180.97.33.107: seq=0 ttl=55 time=87.532 ms