一.正向解析与反向解析
正向解析:根据主机名(域名)查找对应的 IP 地址。
反向解析:根据 IP 地址查找对应的主机名(域名)。（ 反向解析的作用是将用户提交的 IP 地址
解析为对应的域名信息，它一般用于对某个 IP 地址上绑定的所有域名进行整体屏蔽，屏蔽
由某些域名发送的垃圾邮件。也可以判断某虚拟主机上运行了多少个网站。）

正向区域
(1)创建转发域
修改DNS配置文件在主节点拷贝模板文件 named.localhost 到 testmail.com.zone

[root@dns named]# cp -rf named.localhost testmail.com.zone

（2）编辑 testmail.com.zone 文件

[`root@`dns named]# vi testmail.com.zone`

（3）赋予权限
[root@dns named]# chmod 755 testmail.com.zone
（4）修改区域配置文件

vi/etc/named.rfc1912.zones

正向解析
在最后添加zone “testmail.com” IN {
type master;
file “testmail.com.zone”;
};

（5）检验配置

[root@dns named]# named-checkconf /etc/named.conf
[root@dns named]# named-checkzone testmail.com. testmail.com.zone
zone testmail.com/IN: loaded serial 0
OK

生效配置文件
[root@dns named]# systemctl restart named
ping不通dns做一下解析

root@dns named]# ping dns.testmail.com
ping: unknown host dns.testmail.com
添加/etc/resolv.conf 域名服务器 IP
[root@dns named]# vi /etc/resolv.conf
#Generated by NetworkManager
nameserver 192.168.200.99
namesserver 192.168.100.39
nameserver 114.114.114.114
~
``

再次ping可以ping通

[root@dns named]# ping dns.testmail.com
PING dns.testmail.com (192.168.200.39) 56(84) bytes of data.
64 bytes from 192.168.200.39: icmp_seq=1 ttl=64 time=0.649 ms

配置反向解析
（6）修改区域配置文件

[root@dns named]# vi /etc/named.rfc1912.zones

添加zone “200.168.192.in-addr.arpa” IN {
type master;
file “39.200.168.192.in-addr.arpa.local”;
};

[root@dns named]# cp -p testmail.com.zone 39.200.168.192.in-addr.arpa.local

``
（7）配置 39.200.168.192.in-addr.arpa.local

[root@dns named]# vi  39.200.168.192.in-addr.arpa.local

``

添加修改
IN NS dns.testmail.com.
39 IN PTR mail.testmil.com.
39 IN PTR www.testmil.com.
（8）授权

``

[root@dns named]# chmod  755 39.200.168.192.in-addr.arpa.local

``

（9）检验

[root@dns named]# named-checkzone mail.testmail.com 39.200.168.192.in-addr.arpa.local
zone dns.testmail.com/IN: loaded serial 0
OK

``

（10）重启
[root@dns named]# systemctl restart named
``
（11）添加/etc/resolv.conf 域名服务器 IP

[root@mail ~]# vi /etc/resolv.conf

添加nameserver 192.168.200.99
namesserver 192.168.100.39
（11）测试解析是否正常

[root@dns named]# dig -x 192.168.200.39

; <<>> DiG 9.9.4-RedHat-9.9.4-29.el7 <<>> -x 192.168.200.39
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 37403
;; flags: qr aa rd ra; QUERY: 1, ANSWER: 2, AUTHORITY: 1, ADDITIONAL: 2

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
;; QUESTION SECTION:
;39.200.168.192.in-addr.arpa.   IN      PTR

;; ANSWER SECTION:
39.200.168.192.in-addr.arpa. 86400 IN   PTR     mail.testmil.com.
39.200.168.192.in-addr.arpa. 86400 IN   PTR     www.testmil.com.

;; AUTHORITY SECTION:
200.168.192.in-addr.arpa. 86400 IN      NS      dns.testmail.com.

;; ADDITIONAL SECTION:
dns.testmail.com.       86400   IN      A       192.168.200.39

;; Query time: 2 msec
;; SERVER: 192.168.200.99#53(192.168.200.99)
;; WHEN: Thu Jan 28 08:16:06 CST 2021
;; MSG SIZE  rcvd: 147
``

``