双网卡虚拟机不能上网问题: unknown host www.baidu.com

gdfgd

环境：
配置了两块网卡，分为内网和外网;
内网：host-only 模式 192.168.142.140
外网：NAT模式   192.168.116.140
配置文件：

网卡配置文件： [iyunv@yum network-scripts]# cat ifcfg-eth0 DEVICE=eth0 TYPE=Ethernet ONBOOT=yes NM_CONTROLLED=yes BOOTPROTO=dhcp [iyunv@yum network-scripts]# cat ifcfg-eth1 DEVICE=eth1 TYPE=Ethernet ONBOOT=yes NM_CONTROLLED=yes BOOTPROTO=dhcp DNS配置文件： [iyunv@yum network-scripts]# cat /etc/resolv.conf ; generated by /sbin/dhclient-script search localdomain nameserver 192.168.142.1

故障描述：
ping网关和百度的ip都可以ping通，但是ping百度的域名 www.baidu.com 不通，返回ping: unknown host www.baidu.com
故障分析：DNS解析问题
ip地址为DHCP,DNS被192.168.142.1占用，命令行里改了好多次都不管用

[iyunv@Jump ~]# ping www.baidu.com ping: unknown host www.baidu.com [iyunv@Jump ~]# ping www.baidu.com ping: unknown host www.baidu.com [iyunv@Jump ~]# ping 119.75.218.70 PING 119.75.218.70 (119.75.218.70) 56(84) bytes of data. 64 bytes from 119.75.218.70: icmp_seq=1 ttl=128 time=10.6 ms 64 bytes from 119.75.218.70: icmp_seq=2 ttl=128 time=5.69 ms 64 bytes from 119.75.218.70: icmp_seq=3 ttl=128 time=5.39 ms 64 bytes from 119.75.218.70: icmp_seq=4 ttl=128 time=13.2 ms 64 bytes from 119.75.218.70: icmp_seq=5 ttl=128 time=7.67 ms 64 bytes from 119.75.218.70: icmp_seq=6 ttl=128 time=9.23 ms 64 bytes from 119.75.218.70: icmp_seq=7 ttl=128 time=34.4 ms 64 bytes from 119.75.218.70: icmp_seq=8 ttl=128 time=12.0 ms ^C --- 119.75.218.70 ping statistics --- 8 packets transmitted, 8 received, 0% packet loss, time 7382ms rtt min/avg/max/mdev = 5.395/12.299/34.452/8.780 ms

故障解决：
setup   启动图形界面的网卡配置，重新配置ip地址；
配置成功后的配置文件如下：

[iyunv@Jump network-scripts]# cat ifcfg-eth0 DEVICE=eth0 TYPE=Ethernet ONBOOT=yes NM_CONTROLLED=yes BOOTPROTO=none IPADDR=192.168.116.140 NETMASK=255.255.255.0 GATEWAY=192.168.116.2 DNS1=192.168.116.2 HWADDR=00:0c:29:5c:fe:67 IPV6INIT=no USERCTL=no [iyunv@Jump network-scripts]# cat ifcfg-eth1 DEVICE=eth1 TYPE=Ethernet ONBOOT=yes NM_CONTROLLED=yes BOOTPROTO=none IPV6INIT=no USERCTL=no HWADDR=00:0c:29:5c:fe:71 IPADDR=192.168.142.140 NETMASK=255.255.255.0 [iyunv@Jump network-scripts]#

测试：

[iyunv@Jump network-scripts]# ping www.baidu.com PING www.baidu.com (119.75.217.109) 56(84) bytes of data. 64 bytes from 119.75.217.109: icmp_seq=1 ttl=128 time=456 ms 64 bytes from 119.75.217.109: icmp_seq=2 ttl=128 time=336 ms 64 bytes from 119.75.217.109: icmp_seq=3 ttl=128 time=1280 ms 64 bytes from 119.75.217.109: icmp_seq=4 ttl=128 time=336 ms 64 bytes from 119.75.217.109: icmp_seq=5 ttl=128 time=402 ms ^C --- www.baidu.com ping statistics --- 5 packets transmitted, 5 received, 0% packet loss, time 5380ms rtt min/avg/max/mdev = 336.635/562.425/1280.376/361.756 ms, pipe 2

在此感谢李想同学。
排错思路：
unknown host www.baidu.com是DNS问题；ping网关能pingt，ping百度ip也能ping通。确定是DNS问题；
修改配置文件ifcfg-eth0   、DNS 配置文件、setup重新配置网卡
相关原理：DNS原理

setup 回车，选择network configuration回车，    DNS configuration回车（修改DNS） DNS修改为192.168.116.2。OK退出   Device configuration 修改ip地址    “*”号按空格则取消，如下   第二块网卡(内网)无需配网关和DNS 保存退出，重启网络服务