Linux ping:unknown host问题排查

一、检查网卡配置:
输入ifconfig可以查看当前网卡配置的IP地址并且查看配置文件中网络的设置：

[root@bqh- ~]# ifconfig
eth0      Link encap:Ethernet  HWaddr :0C:::FC:1E
          inet addr:192.168.0.117  Bcast:192.168.0.255  Mask:255.255.255.0
          inet6 addr: fe80::20c:29ff:fe71:fc1e/ Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:  Metric:
          RX packets: errors: dropped: overruns: frame:
          TX packets: errors: dropped: overruns: carrier:
          collisions: txqueuelen:
          RX bytes: (52.1 KiB)  TX bytes: (31.1 KiB)

lo        Link encap:Local Loopback
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::/ Scope:Host
          UP LOOPBACK RUNNING  MTU:  Metric:
          RX packets: errors: dropped: overruns: frame:
          TX packets: errors: dropped: overruns: carrier:
          collisions: txqueuelen:
          RX bytes: (0.0 b)  TX bytes: (0.0 b)

[root@bqh- ~]# cat /etc/sysconfig/network-scripts/ifcfg-eth0   #若没有，手动添加即可
DEVICE=eth0
HWADDR=:0C:::FC:1E
TYPE=Ethernet
UUID=d1518dbb-7e56-46f3-94e4-f59927222526
ONBOOT=yes
NM_CONTROLLED=yes
BOOTPROTO=static
IPADDR=192.168.0.117
NETMASK=255.255.255.0
GATEWAY=192.168.0.1

二、检查网卡网关设置:

[root@bqh- ~]# route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
192.168.0.0     0.0.0.0         255.255.255.0   U                    eth0
169.254.0.0     0.0.0.0         255.255.0.0     U                 eth0
0.0.0.0         192.168.0.1     0.0.0.0         UG                   eth0
[root@bqh- ~]# ping 192.168.0.1
PING 192.168.0.1 (192.168.0.1) () bytes of data.
 bytes from 192.168.0.1: icmp_seq= ttl= time=1.51 ms
 bytes from 192.168.0.1: icmp_seq= ttl= time=1.03 ms
 bytes from 192.168.0.1: icmp_seq= ttl= time=0.961 ms

如果未设置，则通过如下方式增加网关：route add default gw 192.168.0.1

三、查看系统默认的网关(如果没有，可以vim手动添加一个上去)

[root@bqh- ~]# cat /etc/sysconfig/network
NETWORKING=yes
HOSTNAME=bqh-
[root@bqh- ~]# echo "GATEWAY=192.168.0.1" >>/etc/sysconfig/network
[root@bqh- ~]# cat /etc/sysconfig/network
NETWORKING=yes
HOSTNAME=bqh-
GATEWAY=192.168.0.1
[root@bqh- ~]# ping baidu.com
^C

四、检查DNS设置:

出现 ping:unknown host 提示大部分原因是 linux 设置的DNS解析不了

[root@bqh- ~]# cat /etc/resolv.conf 
nameserver 192.168.43.1
[root@bqh- ~]# sed -i s#43#0#g /etc/resolv.conf
[root@bqh- ~]# cat /etc/resolv.conf
nameserver 192.168.0.1
[root@bqh- ~]# ping www.baidu.com
PING www.a.shifen.com (220.181.38.150) () bytes of data.
 bytes from 220.181.38.150: icmp_seq= ttl= time=14.3 ms
 bytes from 220.181.38.150: icmp_seq= ttl= time=14.4 ms
^C
--- www.a.shifen.com ping statistics ---
 packets transmitted,  received, % packet loss, time 1072ms
rtt min/avg/max/mdev = 14.323/14.403/14.483/0.080 ms

建议域名服务器设置Google的公共DNS服务