解决linux ping: unknown host www.baidu.com

解决linux ping: unknown host www.baidu.com

转自 http://www.cnblogs.com/happyhotty/articles/2539951.html

"ping: unknown host www.baidu.com" 
解决方案： 
   如果某台Linux服务器ping不通域名, 如下提示: 
[root@localhost ~]# ping www.baidu.com
ping: unknown host www.baidu.com

首先确定已经连接上路由器，并且路由器能够访问外网，可以通过访问网关进行确定

[root@localhost ~]# ping 192.168.1.1
PING 192.168.1.1 (192.168.1.1) 56(84) bytes of data.
64 bytes from 192.168.1.1: icmp_seq=1 ttl=64 time=2.96 ms
64 bytes from 192.168.1.1: icmp_seq=2 ttl=64 time=1.75 ms

如果确定网络没问题的情况下, 可以通过如下步骤寻找解决办法: 
1) 确定设置了域名服务器, 没有的话, 建议设置Google的公共DNS服务, 它应该不会出问题的 

[root@localhost ~]# cat /etc/resolv.conf

search localdomain

因为我的DNS没有设置所以导致了ping外网ping不通。将dns添加到该文件中

[root@localhost ~]# vi /etc/resolv.conf

search localdomain
nameserver 202.98.96.68
nameserver 61.139.2.69
~

2) 确保网关已设置 

# grep GATEWAY /etc/sysconfig/network-scripts/ifcfg* 
------------------------------------------------------------------- 
/etc/sysconfig/network-scripts/ifcfg-eth0:GATEWAY=192.168.40.1 
------------------------------------------------------------------- 

如果未设置, 则通过如下方式增加网关: 

# route add default gw 192.168.40.1 

或者手工编写/etc/sysconfig/network-scripts/ifcfg*文件后, 重启network服务: 

# service network restart 

3) 确保可用dns解析 

# grep hosts /etc/nsswitch.conf 
------------------------------------------------------------------- 
hosts:      files dns 
------------------------------------------------------------------- 

如果以上哪个有问题, 修正后, 再测试, 应该就没问题了: 

#ping -c 3 www.baidu.com 
PING www.a.shifen.com (220.181.6.175) 56(84) bytes of data. 
64 bytes from 220.181.6.175: icmp_seq=0 ttl=50 time=9.51 ms 
64 bytes from 220.181.6.175: icmp_seq=1 ttl=50 time=8.45 ms 
64 bytes from 220.181.6.175: icmp_seq=2 ttl=50 time=8.97 ms 
--- www.a.shifen.com ping statistics --- 
3 packets transmitted, 3 received, 0% packet loss, time 2002ms 
rtt min/avg/max/mdev = 8.450/8.977/9.511/0.446 ms, pipe 2