centos系统外网网卡关闭如何访问外网?

Question

目前服务器外网网卡是关闭状态。执行ifconfig命令如下：

[root@appserv3 lala]# ifconfig 
eth1: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet xx.xx.xx.xx  netmask 255.255.255.0  broadcast xx.xx.xx.xx
        inet6 xxxx::xxxx:xxxx:xxxx:xxxx  prefixlen 64  scopeid 0x20<link>
        ether xx:xx:xx:xx:xx:xx  txqueuelen 1000  (Ethernet)
        RX packets 59294369  bytes 19475249493 (18.1 GiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 48539353  bytes 11472370873 (10.6 GiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0
        device interrupt 50  

lo: flags=73<UP,LOOPBACK,RUNNING>  mtu 65536
        inet 127.0.0.1  netmask 255.0.0.0
        inet6 ::1  prefixlen 128  scopeid 0x10<host>
        loop  txqueuelen 1  (Local Loopback)
        RX packets 9648082  bytes 575069270 (548.4 MiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 9648082  bytes 575069270 (548.4 MiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

而在该情况下ping外网是ping不通的，如ping www.baidu.com，提示connect: network is unreachable。
后来在/etc/resolv.conf文件中加了一个nameserver配置信息后，再次ping时提示

PING www.a.shifen.com (61.135.169.125) 56(84) bytes of data.

--- www.a.shifen.com ping statistics ---
4 packets transmitted, 0 received, 100% packet loss, time 2999ms

请问如何解决该问题使得在外网网卡关闭情况下成功访问外网呢？

Answer 1

你这都 100% loss 了，哪里成功访问外网了？

你这指定的 nameserver 应该是个内网的 DNS 服务器吧？ping 的时候域名会先经过 DNS 解析成 IP，然后 ICMP 这个 IP。

第一步 DNS 解析肯定是通的啊，你这都有一个内网的 DNS 服务器了；第二步 ICMP 挂了啊，都没外网网卡，当然访问不到外网啊。