1. 用户访问网站流程

DNS基础知识 - 图1

2. 通过命令理解DNS

2.1 dig

参数选项: [@server] [-b address] [-p port#] [-q name] [-t type]
[root@oldboy ~]# dig @8.8.8.8 www.baidu.com +trace

; <<>> DiG 9.8.2rc1-RedHat-9.8.2-0.17.rc1.el6_4.6 <<>> @8.8.8.8 www.baidu.com +trace
; (1 server found)
;; global options: +cmd
. 11733 IN NS a.root-servers.net.
. 11733 IN NS b.root-servers.net.
. 11733 IN NS c.root-servers.net.
. 11733 IN NS d.root-servers.net.
. 11733 IN NS e.root-servers.net.
. 11733 IN NS f.root-servers.net.
. 11733 IN NS g.root-servers.net.
. 11733 IN NS h.root-servers.net.
. 11733 IN NS i.root-servers.net.
. 11733 IN NS j.root-servers.net.
. 11733 IN NS k.root-servers.net.
. 11733 IN NS l.root-servers.net.
. 11733 IN NS m.root-servers.net.
;; Received 228 bytes from 8.8.8.8#53(8.8.8.8) in 65300 ms

com. 172800 IN NS l.gtld-servers.net.
com. 172800 IN NS h.gtld-servers.net.
com. 172800 IN NS b.gtld-servers.net.
com. 172800 IN NS a.gtld-servers.net.
com. 172800 IN NS g.gtld-servers.net.
com. 172800 IN NS d.gtld-servers.net.
com. 172800 IN NS k.gtld-servers.net.
com. 172800 IN NS i.gtld-servers.net.
com. 172800 IN NS c.gtld-servers.net.
com. 172800 IN NS f.gtld-servers.net.
com. 172800 IN NS e.gtld-servers.net.
com. 172800 IN NS j.gtld-servers.net.
com. 172800 IN NS m.gtld-servers.net.
;; Received 491 bytes from 192.228.79.201#53(192.228.79.201) in 65894 ms

baidu.com. 172800 IN NS dns.baidu.com.
baidu.com. 172800 IN NS ns2.baidu.com.
baidu.com. 172800 IN NS ns3.baidu.com.
baidu.com. 172800 IN NS ns4.baidu.com.
baidu.com. 172800 IN NS ns7.baidu.com.
;; Received 201 bytes from 192.33.14.30#53(192.33.14.30) in 25260 ms

www.baidu.com. 1200 IN CNAME www.a.shifen.com.
a.shifen.com. 1200 IN NS ns3.a.shifen.com.
a.shifen.com. 1200 IN NS ns1.a.shifen.com.
a.shifen.com. 1200 IN NS ns5.a.shifen.com.
a.shifen.com. 1200 IN NS ns2.a.shifen.com.
a.shifen.com. 1200 IN NS ns4.a.shifen.com.
;; Received 228 bytes from 119.75.219.82#53(119.75.219.82) in 26 ms

2.2 nslookup

[root@oldboy ~]# nslookup
> www.linux.ac.cn
Server: 119.29.29.29
Address: 119.29.29.29#53

Non-authoritative answer:
Name: www.linux.ac.cn
Address: 115.159.144.103

2.3 host

[root@oldboy ~]# host www.linux.ac.cn
www.linux.ac.cn has address 115.159.144.103

2.4 ping

[root@oldboy ~]# ping www.linux.ac.cn
PING www.linux.ac.cn (115.159.144.103) 56(84) bytes of data.