在Uboot下还没有关闭防火墙前
OpenJTAG> ping 192.168.88.226
ERROR: resetting DM9000 -> not responding
dm9000 i/o: 0x20000000, id: 0x90000a46
DM9000: running in 16 bit mode
MAC: 08:00:3e:26:0a:5b
could not establish link
checksum bad
ping failed; host 192.168.88.226 is not alive
在Uboot下关闭防火墙后
OpenJTAG> ping 192.168.88.226
ERROR: resetting DM9000 -> not responding
dm9000 i/o: 0x20000000, id: 0x90000a46
DM9000: running in 16 bit mode
MAC: 08:00:3e:26:0a:5b
could not establish link
host 192.168.88.226 is alive
根据网上的说法如果看到 host 某某 is alive，说明是通的。
在启动kernel后，未关闭防火墙，ping百度（119.75.217.56）无法ping通
# ping 119.75.217.56
PING 119.75.217.56 (119.75.217.56): 56 data bytes
ping: sendto: Network is unreachable
ping不通是因为我的开发板设置的IP和路由器不在同一网段，并且网关也需要设置对
先查询当前的ip看是不是和路由器同一网段
# ifconfig
eth0 Link encap:Ethernet HWaddr 00:60:6E:33:44:55
inet addr:192.168.1.17 Bcast:192.168.1.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:18 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:1440 (1.4 KiB) TX bytes:0 (0.0 B)
Interrupt:51 Base address:0xa000
将开发板设置为和电脑同一网段，并设置默认网关
# ifconfig eth0 192.168.88.158
设置默认网关
# route add default gw 192.168.88.1
查看设置后的IP和默认网关是否正确
# ifconfig
eth0 Link encap:Ethernet HWaddr 00:60:6E:33:44:55
inet addr:192.168.88.158 Bcast:192.168.88.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:29 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:2336 (2.2 KiB) TX bytes:0 (0.0 B)
Interrupt:51 Base address:0xa000
确保正确后，继续ping百度（ping 119.75.217.56）
# ping 119.75.217.56
PING 119.75.217.56 (119.75.217.56): 56 data bytes
64 bytes from 119.75.217.56: seq=0 ttl=55 time=42.313 ms
64 bytes from 119.75.217.56: seq=1 ttl=55 time=36.514 ms
64 bytes from 119.75.217.56: seq=2 ttl=55 time=36.649 ms
64 bytes from 119.75.217.56: seq=3 ttl=55 time=36.561 ms
有数据回复证明已经成功ping通百度，能ping通外网按理来说应该是可以ping通电脑的，但出乎我的意料
# ping 192.168.88.226
PING 192.168.88.226 (192.168.88.226): 56 data bytes
返回数据让我傻眼，百度了很久还是没有找到原理，后来看到百度：开发板ping 不通电脑，看到有防火墙问题，于是尝试关闭防火墙，关闭防火墙后在去ping电脑（关闭防火墙步骤：控制面板-_>系统和安全-->Windows 防火墙-->打开或关闭防火墙-->关闭window防火墙-->确定，注意家庭和公共网络两个地方都关闭）
# ping 192.168.88.226
PING 192.168.88.226 (192.168.88.226): 56 data bytes
64 bytes from 192.168.88.226: seq=0 ttl=128 time=1.299 ms
64 bytes from 192.168.88.226: seq=1 ttl=128 time=1.307 ms
64 bytes from 192.168.88.226: seq=2 ttl=128 time=2.443 ms
64 bytes from 192.168.88.226: seq=3 ttl=128 time=1.840 ms
看到这个数据我高兴起来了，因为已经ping通电脑
参考
https://blog.csdn.net/thisway_diy/article/details/88184822