DNS解析及轮询
一、DNS排错
NOERROR ###查询成功
NXDOMAIN ###DNS服务器提示不存在这样的名称
SERVFAIL ###DNS服务器停机或DNSSEC响应验证失败
REFUSED ###DNS服务器拒绝回答二、高速缓存DNS
虚拟机IP:172.25.254.125(服务器)
selinux iptables off
1、安装DNS
yum install bind.x86_64 -y
systemctl start named ###启动服务
cat /etc/rndc.key ###开始不存在，服务启动建立
cat /etc/services |grep domain ###查看DNS的端口2、配置named.conf
vim /etc/named.conf
10 options {
11 listen-on port 53 { any; }; ###开启53端口访问
12 listen-on-v6 port 53 { ::1; };
13 directory "/var/named";
14 dump-file "/var/named/data/cache_dump.db";
15 statistics-file "/var/named/data/named_stats.txt";
16 memstatistics-file "/var/named/data/named_mem_stats.txt";
17 allow-query { any; }; ###允许所有人访问
18 forwarders { 172.25.254.250; }; ###如果没有就访问172.25.254.250
19 /*
systemctl restart named3、测试
虚拟机IP:172.25.254.225
vim /etc/resolv.conf
nameserver 172.25.254.125
虚拟机IP:172.25.254.56
vim /etc/resolv.conf
nameserver 172.25.254.125测试结果：2台分别访问dig www.baidu.com，可以发现第一次慢，第二次快
三、DNS正向解析
原理：将域名转化为IP地址
1、配置named.conf
虚拟机IP:172.25.254.125(服务器)
vim /etc/named.conf
10 options {
11 listen-on port 53 { any; }; ###开启53端口访问
12 listen-on-v6 port 53 { ::1; };
13 directory "/var/named";
14 dump-file "/var/named/data/cache_dump.db";
15 statistics-file "/var/named/data/named_stats.txt";
16 memstatistics-file "/var/named/data/named_mem_stats.txt";
17 allow-query { any; }; ###允许所有人访问
18 /* 2、配置named.rfc1912.zones
vim /etc/named.rfc1912.zones
19 zone "localhost" IN { ###y6y复制，p粘贴
20 type master;
21 file "named.localhost";
22 allow-update { none; };
23 };
24
25 zone "dream.com" IN {
26 type master;
27 file "dream.com.zone"; ###访问的文件
28 allow-update { none; };
29 };
cp -p /var/named/named.localhost /var/named/dream.com.zone3、配置dream.com.zone
vim /var/named/dream.com.zone ###结尾加点表示结束，如果没有会补（.dream.com）
1 $TTL 1D
2 @ IN SOA dns.dream.com. root.dream.com. (
3 0 ; serial
4 1D ; refresh
5 1H ; retry
6 1W ; expire
7 3H ) ; minimum
8 NS dns.dream.com. ###nameserver:下面指向服务器的IP
9 dns A 172.25.254.125
10 www A 172.25.254.225 ###把www.dream.com解析到172.25.254.225这个IP4、测试
真机IP:172.25.254.56
vim /etc/resolv.conf
nameserver 172.25.254.125
dig www.dream.com
四、DNS轮询
注意：此功能DNS自带，在DNS正向解析的条件下！！！
1、配置dream.com.zone
vim /var/named/dream.com.zone
1 $TTL 1D
2 @ IN SOA dns.dream.com. root.dream.com. (
3 0 ; serial
4 1D ; refresh
5 1H ; retry
6 1W ; expire
7 3H ) ; minimum
8 NS dns.dream.com.
9 dns A 172.25.254.125
10 www CNAME login.dream.com.
11 login A 172.25.254.225
12 login A 172.25.254.56
systemctl restart named2、测试
真机IP:172.25.254.56
dig www.dream.com
五、DNS反向解析
原理：将IP地址转化为域名
在DNS正向解析的条件下,虚拟机IP:172.25.254.125(服务器)
1、配置named.rfc1912.zones
vim /etc/named.rfc1912.zones
43 zone "0.in-addr.arpa" IN {
44 type master;
45 file "named.empty";
46 allow-update { none; };
47 };
48
49 zone "254.25.172.in-addr.arpa" IN {
50 type master;
51 file "dream.com.ptr";
52 allow-update { none; };
53 };
cp -p /var/named/named.loopback /var/named/dream.com.ptr2、配置dream.com.ptr
vim /var/named/dream.com.ptr
1 $TTL 1D
2 @ IN SOA dns.dream.com. root.dream.com. (
3 0 ; serial
4 1D ; refresh
5 1H ; retry
6 1W ; expire
7 3H ) ; minimum
8 NS dns.dream.com.
9 dns A 172.25.254.125
10 225 PTR www.dream.com
11 56 PTR login.dream.com
systemctl restart named3、测试
真机IP:172.25.254.56
dig -x 172.25.254.56 ###反向解析到login.dream.com
dig -x 172.25.254.225 ###反向解析到www.dream.com
六、DNS双向解析
运用DNS双向解析，我们可以让内外网访问的网段不同。这里我们以外网访问172.25.254网段，内网访问192.25.254网段为例。
1、配置dream.com.inter
cp -p /var/named/dream.com.zone /var/named/dream.com.inter
vim /var/named/dream.com.inter
1 $TTL 1D
2 @ IN SOA dns.dream.com. root.dream.com. (
3 0 ; serial
4 1D ; refresh
5 1H ; retry
6 1W ; expire
7 3H ) ; minimum
8 NS dns.dream.com.
9 dns A 192.25.254.125
10 www CNAME login.dream.com.
11 login A 192.25.254.225
12 login A 192.25.254.562、配置named.rfc1912.zones.inter
cp -p /etc/named.rfc1912.zones /etc/named.rfc1912.zones.inter
vim /etc/named.rfc1912.zones.inter
25 zone "dream.com" IN {
26 type master;
27 file "dream.com.inter";
28 allow-update { none; };
29 };3、配置named.conf
vim /etc/named.conf
51 #zone "." IN {
52 # type hint;
53 # file "named.ca";
54 #};
55 #
56 #include "/etc/named.rfc1912.zones";
57 #include "/etc/named.root.key";
58 view localnet {
59 match-clients { 172.25.254.125; }; ###这里为了测试方便把125当成内网，其他为外网。应该写localhost
60 zone "." IN {
61 type hint;
62 file "named.ca";
63 };
64 include "/etc/named.rfc1912.zones.inter";
65 };
66 view internet {
67 match-clients { any; };
68 zone "." IN {
69 type hint;
70 file "named.ca";
71 };
72 include "/etc/named.rfc1912.zones";
73 };
systemctl restart named4、测试
（1）在IP：172.25.254.125（服务器）中/etc/resolv.conf加入nameserver 172.25.254.125，dig www.dream.com
（2）在IP：172.25.254.225中dig www.dream.com
