DNS记录(NS\A\MX记录)查询工具 ：nslookup和dig(2)

. 518138 IN NS A.ROOT-SERVERS.NET.
. 518138 IN NS B.ROOT-SERVERS.NET.
. 518138 IN NS C.ROOT-SERVERS.NET.
. 518138 IN NS D.ROOT-SERVERS.NET.
. 518138 IN NS E.ROOT-SERVERS.NET.
. 518138 IN NS F.ROOT-SERVERS.NET.
. 518138 IN NS G.ROOT-SERVERS.NET.
. 518138 IN NS H.ROOT-SERVERS.NET.
. 518138 IN NS I.ROOT-SERVERS.NET.
. 518138 IN NS J.ROOT-SERVERS.NET.
. 518138 IN NS K.ROOT-SERVERS.NET.
. 518138 IN NS L.ROOT-SERVERS.NET.
. 518138 IN NS M.ROOT-SERVERS.NET.
;; Received 228 bytes from 192.168.1.1#53(192.168.1.1) in 15 ms

cn. 172800 IN NS C.DNS.cn.
cn. 172800 IN NS D.DNS.cn.
cn. 172800 IN NS E.DNS.cn.
cn. 172800 IN NS NS.CERNET.NET.
cn. 172800 IN NS A.DNS.cn.
cn. 172800 IN NS B.DNS.cn.
;; Received 297 bytes from 198.41.0.4#53(A.ROOT-SERVERS.NET) in 281 ms

sina.com.cn. 21600 IN NS ns3.sina.com.cn.
sina.com.cn. 21600 IN NS ns1.sina.com.cn.
sina.com.cn. 21600 IN NS ns2.sina.com.cn.
;; Received 136 bytes from 203.119.29.1#53(E.DNS.cn) in 171 ms

news.sina.com.cn. 60 IN CNAME jupiter.sina.com.cn.
jupiter.sina.com.cn. 60 IN CNAME hydra.sina.com.cn.
hydra.sina.com.cn. 60 IN A 218.30.108.61
hydra.sina.com.cn. 60 IN A 218.30.108.62
hydra.sina.com.cn. 60 IN A 218.30.108.63
hydra.sina.com.cn. 60 IN A 218.30.108.64
hydra.sina.com.cn. 60 IN A 218.30.108.65
hydra.sina.com.cn. 60 IN A 218.30.108.66
hydra.sina.com.cn. 60 IN A 218.30.108.67
hydra.sina.com.cn. 60 IN A 218.30.108.68
hydra.sina.com.cn. 60 IN A 218.30.108.69
hydra.sina.com.cn. 60 IN A 218.30.108.72
hydra.sina.com.cn. 60 IN A 218.30.108.73
hydra.sina.com.cn. 60 IN A 218.30.108.74
hydra.sina.com.cn. 60 IN A 218.30.108.55
hydra.sina.com.cn. 60 IN A 218.30.108.56
hydra.sina.com.cn. 60 IN A 218.30.108.57
hydra.sina.com.cn. 60 IN A 218.30.108.58
sina.com.cn. 86400 IN NS ns1.sina.com.cn.
sina.com.cn. 86400 IN NS ns2.sina.com.cn.
sina.com.cn. 86400 IN NS ns3.sina.com.cn.
;; Received 434 bytes from 202.106.184.166#53(ns1.sina.com.cn) in 31 ms

从上面的记录，我们可以看到整个的流程，从根服务器查询到cn的根服务器，然后查询到sina.com.cn的名字服务器，
news.sina.com.cn -> jupiter.sina.com.cn -->hydra.sina.com.cn 最后得到hydra的服务器IP。