如何获得可用的谷歌IP

这里我们使用强大的dig工具，trace参数是指从根服务器开始查询。dns是使用V2EX的dns://178.79.131.110 和谷歌dns://8.8.4.4.
接下来打开终端开始查询。
v2ex的dns（日本的linode搭建）查询到跟服务器就断了，说明它不是一个真正的dns服务器，而是返回其他正规dns服务器的结果。

C:\Users\Jings>dig +trace google.com @178.79.131.110
; <<>> DiG 9.3.2 <<>> +trace google.com @178.79.131.110
; (1 server found)
;; global options:  printcmd
.                       16252   IN      NS      a.root-servers.net.
.                       16252   IN      NS      b.root-servers.net.
.                       16252   IN      NS      c.root-servers.net.
.                       16252   IN      NS      d.root-servers.net.
.                       16252   IN      NS      e.root-servers.net.
.                       16252   IN      NS      f.root-servers.net.
.                       16252   IN      NS      g.root-servers.net.
.                       16252   IN      NS      h.root-servers.net.
.                       16252   IN      NS      i.root-servers.net.
.                       16252   IN      NS      j.root-servers.net.
.                       16252   IN      NS      k.root-servers.net.
.                       16252   IN      NS      l.root-servers.net.
.                       16252   IN      NS      m.root-servers.net.
;; Received 228 bytes from 178.79.131.110#53(178.79.131.110) in 1466 ms
com.                    172800  IN      NS      a.gtld-servers.net.
com.                    172800  IN      NS      b.gtld-servers.net.
com.                    172800  IN      NS      c.gtld-servers.net.
com.                    172800  IN      NS      d.gtld-servers.net.
com.                    172800  IN      NS      e.gtld-servers.net.
com.                    172800  IN      NS      f.gtld-servers.net.
com.                    172800  IN      NS      g.gtld-servers.net.
com.                    172800  IN      NS      h.gtld-servers.net.
com.                    172800  IN      NS      i.gtld-servers.net.
com.                    172800  IN      NS      j.gtld-servers.net.
com.                    172800  IN      NS      k.gtld-servers.net.
com.                    172800  IN      NS      l.gtld-servers.net.
com.                    172800  IN      NS      m.gtld-servers.net.
;; Received 488 bytes from 198.41.0.4#53(a.root-servers.net) in 1201 ms
dig: couldn't get address for 'b.gtld-servers.net': not found

下面是正规的谷歌dns，返回的结果正好是四步下来（四个时间戳）。
这是属于dns挟持，而dns污染则是只能显示两步就给出一个错误的ip给用户。
但我们发现，最后的结果确实是谷歌服务器，但是无法访问。

C:\Users\Jings>dig +trace google.com @8.8.4.4
; <<>> DiG 9.3.2 <<>> +trace google.com @8.8.4.4
; (1 server found)
;; global options:  printcmd
.                       20741   IN      NS      g.root-servers.net.
.                       20741   IN      NS      m.root-servers.net.
.                       20741   IN      NS      d.root-servers.net.
.                       20741   IN      NS      f.root-servers.net.
.                       20741   IN      NS      c.root-servers.net.
.                       20741   IN      NS      l.root-servers.net.
.                       20741   IN      NS      a.root-servers.net.
.                       20741   IN      NS      k.root-servers.net.
.                       20741   IN      NS      e.root-servers.net.
.                       20741   IN      NS      j.root-servers.net.
.                       20741   IN      NS      h.root-servers.net.
.                       20741   IN      NS      b.root-servers.net.
.                       20741   IN      NS      i.root-servers.net.
;; Received 228 bytes from 8.8.4.4#53(8.8.4.4) in 249 ms
com.                    172800  IN      NS      d.gtld-servers.net.
com.                    172800  IN      NS      m.gtld-servers.net.
com.                    172800  IN      NS      a.gtld-servers.net.
com.                    172800  IN      NS      j.gtld-servers.net.
com.                    172800  IN      NS      h.gtld-servers.net.
com.                    172800  IN      NS      l.gtld-servers.net.
com.                    172800  IN      NS      i.gtld-servers.net.
com.                    172800  IN      NS      g.gtld-servers.net.
com.                    172800  IN      NS      k.gtld-servers.net.
com.                    172800  IN      NS      f.gtld-servers.net.
com.                    172800  IN      NS      c.gtld-servers.net.
com.                    172800  IN      NS      b.gtld-servers.net.
com.                    172800  IN      NS      e.gtld-servers.net.
;; Received 488 bytes from 192.112.36.4#53(g.root-servers.net) in 265 m
google.com.             172800  IN      NS      ns2.google.com.
google.com.             172800  IN      NS      ns1.google.com.
google.com.             172800  IN      NS      ns3.google.com.
google.com.             172800  IN      NS      ns4.google.com.
;; Received 164 bytes from 192.5.6.30#53(a.gtld-servers.net) in 265 ms
google.com.             300     IN      A       173.194.127.192
google.com.             300     IN      A       173.194.127.193
google.com.             300     IN      A       173.194.127.201
google.com.             300     IN      A       173.194.127.197
google.com.             300     IN      A       173.194.127.196
google.com.             300     IN      A       173.194.127.195
google.com.             300     IN      A       173.194.127.194
google.com.             300     IN      A       173.194.127.198
google.com.             300     IN      A       173.194.127.200
google.com.             300     IN      A       173.194.127.206
google.com.             300     IN      A       173.194.127.199
;; Received 204 bytes from 216.239.34.10#53(ns2.google.com) in 218 ms

那么我们怎么获得可用的谷歌ip地址呢？
这里还是使用dig，由于windows没有自带dig，但是有自带nslookup，nslookup也可以。

• 查询 google.com有效ip
  
  • dig法

C:\Users\Jings>dig google.com @178.79.131.110
; <<>> DiG 9.3.2 <<>> google.com @178.79.131.110
; (1 server found)
;; global options:  printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 1962
;; flags: qr rd ra; QUERY: 1, ANSWER: 11, AUTHORITY: 0, ADDITIO
;; QUESTION SECTION:
;google.com.                    IN      A
;; ANSWER SECTION:
google.com.             105     IN      A       74.125.230.229
google.com.             105     IN      A       74.125.230.238
google.com.             105     IN      A       74.125.230.232
google.com.             105     IN      A       74.125.230.227
google.com.             105     IN      A       74.125.230.228
google.com.             105     IN      A       74.125.230.231
google.com.             105     IN      A       74.125.230.230
google.com.             105     IN      A       74.125.230.226
google.com.             105     IN      A       74.125.230.233
google.com.             105     IN      A       74.125.230.224
google.com.             105     IN      A       74.125.230.225
;; Query time: 483 msec
;; SERVER: 178.79.131.110#53(178.79.131.110)
;; WHEN: Thu Jan 01 01:49:13 2015
;; MSG SIZE  rcvd: 204

• • dnslookup法(-vc是指使用TCP查询，由于TCP包更安全结果更准确)

C:\Users\Jings>nslookup -vc ipv4.google.com 178.79.131.110
服务器:  UnKnown
Address:  178.79.131.110
非权威应答:
名称:    ipv4.l.google.com
Addresses:  74.125.230.232
          74.125.230.227
          74.125.230.233
          74.125.230.230
          74.125.230.231
          74.125.230.228
          74.125.230.224
          74.125.230.229
          74.125.230.225
          74.125.230.238
          74.125.230.226
Aliases:  ipv4.google.com

那为什么V2EX的dns解析出来的网站反而能访问呢？
俗话说的好，树大招风，谷歌的dns在国内是被挟持的，而V2EX的dns只是通过过滤掉污染的ip再使用日本的网络以TCP协议的方式解析出可用ip，再把这些ip进行筛选而选出ping值最小的ip段。
搭建类似的dns只需使用如下开源工具搭建即可。
https://github.com/styx-hy/dnsmasq-chinadns