centos7配置DNS(BIND)

DNS简介：

DNS，Domain Name System，域名系统，用于Internet上域名和IP地址的相互映射，使得用户不用记忆主机IP地址，仅通过与之对应的域名就可以访问该主机。

关于BIND软件：

https://www.isc.org/downloads/bind/

下面是本地dns服务器搭建过程 - yum安装bind和bind-utils，后者包含dns查询工具dig

yum install bind bind-utils -y

• 修改配置文件 named.conf

vim /etc/named.conf

修改内容如下：

options {
    //修改监听IP
    listen-on port 53 { any; };
};

//建立正向解析域（本地域）
zone "test.com" IN {
        type master;
        file "test.com.zone";
};

//建立反向解析域（本地域）
zone "3.168.192.in-addr.arpa" IN {
        type master;
        file "3.168.192.zone";
};

检查配置语法正确与否：

named-checkconf

• 创建区域文件

正向解析：

使用named.localhost文件的副本，更改属组为named。

cp named.localhost test.com.zone
chgrp named test.com.zone
vim test.com.zone

test.com.zone 内容如下：

$TTL 1D
    @       IN SOA  @ admin.test.com. (
                                        2017020601       ; serial
                                        1D      ; refresh
                                        1H      ; retry
                                        1W      ; expire
                                        3H )    ; minimum
            NS      ns.test.com.
            MX 5    mail.test.com.
    ns      A       192.168.3.60
    mail    A       192.168.3.61
    www     A       192.168.3.62
    bbs     A       192.168.3.63

检查语法正确与否：

named-checkzone "test.com" /var/named/test.com.zone 

反向解析： 使用named.localhost文件的副本，更改属组为named。

cp named.localhost 3.168.192.zone
chgrp named 3.168.192.zone
vim 3.168.192.zone 

3.168.192.zone 内容如下：

$TTL 1D
@       IN SOA  @ admin.dt.com. (
                                        2017020701      ; serial
                                        1D      ; refresh
                                        1H      ; retry
                                        1W      ; expire
                                        3H )    ; minimum
        IN NS   ns.dt.com.
60      IN PTR  ns.dt.com.
61      IN PTR  mail.dt.com.
62      IN PTR  www.dt.com.
63      IN PTR  bbs.dt.com.

• 启动named，测试dns解析

systemctl start named

$ dig @192.168.3.60 bbs.test.com
; <<>> DiG 9.8.2rc1-RedHat-9.8.2-0.47.rc1.el6_8.4 <<>> @192.168.3.60 bbs.test.com
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 16609
;; flags: qr aa rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 1, ADDITIONAL: 1

;; QUESTION SECTION:
;bbs.test.com.                    IN      A

;; ANSWER SECTION:
bbs.test.com.             86400   IN      A       192.168.3.62

;; AUTHORITY SECTION:
test.com.                 86400   IN      NS      ns.test.com.

;; ADDITIONAL SECTION:
ns.test.com.              86400   IN      A       192.168.3.60

;; Query time: 0 msec
;; SERVER: 192.168.3.60#53(192.168.3.60)
;; WHEN: Wed Feb  8 13:28:57 2017
;; MSG SIZE  rcvd: 77

遇到的问题和解决方法

• 修改完区域文件，重启named，出错：

Error in named configuration:
dns_rdata_fromtext: test.com.zone:10: near 'mail.test.com.': not a valid number
zone test.com/IN: loading from master file test.com.zone failed: not a valid number
zone test.com/IN: not loaded due to errors.
_default/test.com/IN: not a valid number
zone 3.168.192.in-addr.arpa/IN: loaded serial 2017020701
zone localhost.localdomain/IN: loaded serial 0
zone localhost/IN: loaded serial 0
zone 1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa/IN: loaded serial 0
zone 1.0.0.127.in-addr.arpa/IN: loaded serial 0
zone 0.in-addr.arpa/IN: loaded serial 0

原因是正向解析区域文件中，MX记录缺少优先级，由“MX mail.test.com”改为“MX 5 mail.test.com”，不再报错。

• 使用named-checkzone检查区域文件，出错：

dns_rdata_fromtext: /var/named/test.com.zone:3: near '1D': not a valid number
zone test.com/IN: loading from master file /var/named/test.com.zone failed: not a valid number
zone test.com/IN: not loaded due to errors.

解决方法： 在第2行” IN SOA “后、” ( “前，添加” @ “或” test.com. “，正确语句如下：

@       IN SOA    @    admin.test.com. (
...

@       IN SOA    test.com.    admin.test.com. (
...