DNS是什么？
网站输入域名，daxian001 --->10.0.0.10 从域名解析到IP 就绪需要DNS
DNS能干什么
A记录 www.daxian001.com --->10.0.0.10
mx解析记录 123456@qq.com 邮件服务
PTR反向解析 10.0.0.10 -->www.daxian001.com
DNS解析流程原理
DNS解析命令
dig 查看解析过程
dig @8.8.8.8 www.baidu.com +trace
; <<>> DiG 9.8.2rc1-RedHat-9.8.2-0.37.rc1.el6 <<>> @8.8.8.8 www.baidu.com +trace
; (1 server found)
;; global options: +cmd
. 39456 IN NS m.root-servers.net.
. 39456 IN NS c.root-servers.net.
. 39456 IN NS h.root-servers.net.
. 39456 IN NS g.root-servers.net.
. 39456 IN NS k.root-servers.net.
. 39456 IN NS l.root-servers.net.
. 39456 IN NS e.root-servers.net.
. 39456 IN NS i.root-servers.net.
. 39456 IN NS j.root-servers.net.
. 39456 IN NS b.root-servers.net.
. 39456 IN NS d.root-servers.net.
. 39456 IN NS a.root-servers.net.
. 39456 IN NS f.root-servers.net.
;; Received 228 bytes from 8.8.8.8#53(8.8.8.8) in 76 ms
com. 172800 IN NS m.gtld-servers.net.
com. 172800 IN NS a.gtld-servers.net.
com. 172800 IN NS c.gtld-servers.net.
com. 172800 IN NS e.gtld-servers.net.
com. 172800 IN NS h.gtld-servers.net.
com. 172800 IN NS l.gtld-servers.net.
com. 172800 IN NS d.gtld-servers.net.
com. 172800 IN NS k.gtld-servers.net.
com. 172800 IN NS f.gtld-servers.net.
com. 172800 IN NS g.gtld-servers.net.
com. 172800 IN NS b.gtld-servers.net.
com. 172800 IN NS j.gtld-servers.net.
com. 172800 IN NS i.gtld-servers.net.
;; Received 491 bytes from 192.33.4.12#53(192.33.4.12) in 291 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 301 ms
www.baidu.com. 1200 IN CNAME www.a.shifen.com.
a.shifen.com. 1200 IN NS ns4.a.shifen.com.
a.shifen.com. 1200 IN NS ns2.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 ns3.a.shifen.com.
;; Received 228 bytes from 220.181.38.10#53(220.181.38.10) in 7 ms
nslookup解析域名
[root@web01 ~]# nslookup > baidu.com Server: 192.168.20.20 Address: 192.168.20.20#53 Non-authoritative answer: Name: baidu.com Address: 220.181.57.217 Name: baidu.com Address: 123.125.114.144 Name: baidu.com Address: 111.13.101.208
host解析
host www.baidu.com www.baidu.com is an alias for www.a.shifen.com. www.a.shifen.com has address 119.75.213.61 www.a.shifen.com has address 119.75.216.20
ping域名
[root@web01 ~]# ping www.baidu.com PING www.a.shifen.com (119.75.213.61) 56(84) bytes of data. 64 bytes from 119.75.213.61: icmp_seq=1 ttl=53 time=3.94 ms 64 bytes from 119.75.213.61: icmp_seq=2 ttl=53 time=3.26 ms 64 bytes from 119.75.213.61: icmp_seq=3 ttl=53 time=3.33 ms 64 bytes from 119.75.213.61: icmp_seq=4 ttl=53 time=3.55 ms 64 bytes from 119.75.213.61: icmp_seq=5 ttl=53 time=3.27 ms 64 bytes from 119.75.213.61: icmp_seq=6 ttl=53 time=3.44 ms 64 bytes from 119.75.213.61: icmp_seq=7 ttl=53 time=3.24 ms 64 bytes from 119.75.213.61: icmp_seq=8 ttl=53 time=3.47 ms 64 bytes from 119.75.213.61: icmp_seq=9 ttl=53 time=3.39 ms