DNS转发之bind

全局转发

first：先转发至指定DNS服务器，如果无法解析查询请求，则本服务器再去根服务器查询
only: 先转发至指定DNS服务器，如果无法解析查询请求，则本服务器将不再去根服务器查询

17服务器安装软件

[root@localhost ~]# yum install bind -y

改配置文件 only

[root@localhost ~]# vim /etc/named.conf
# 添加下面两条
options {
//  listen-on port 53 { 127.0.0.1; };
    listen-on-v6 port 53 { ::1; };
    directory   "/var/named";
    dump-file   "/var/named/data/cache_dump.db";
    statistics-file "/var/named/data/named_stats.txt";
    memstatistics-file "/var/named/data/named_mem_stats.txt";
    recursing-file  "/var/named/data/named.recursing";
    secroots-file   "/var/named/data/named.secroots";
//  allow-query     { localhost; };
    forward  only;
    forwarders {172.31.0.38;};
    
    dnssec-enable no;
    dnssec-validation no;

开机启动

[root@localhost ~]# systemctl enable --now named

客户端验证

[17:24:13 root@sz-kx-centos8 ~]# dig www.longxuan.vip @172.31.0.17

注意：如果DNS服务器停止了，是做不了转发了

改配置文件 first

[root@localhost ~]# vim /etc/named.conf
options {
//  listen-on port 53 { 127.0.0.1; };
    listen-on-v6 port 53 { ::1; };
    directory   "/var/named";
    dump-file   "/var/named/data/cache_dump.db";
    statistics-file "/var/named/data/named_stats.txt";
    memstatistics-file "/var/named/data/named_mem_stats.txt";
    recursing-file  "/var/named/data/named.recursing";
    secroots-file   "/var/named/data/named.secroots";
//  allow-query     { localhost; };
    forward  first;                                     
    forwarders {172.31.0.38;}; 
    
    dnssec-enable no;
    dnssec-validation no;

重启服务

[root@localhost ~]# rndc reload
server reload successful

DNS服务端删除默认路由

[root@localhost named]# ip route
default via 172.31.0.254 dev eth0 proto static metric 100 
172.31.0.0/16 dev eth0 proto kernel scope link src 172.31.0.38 metric 100 
[root@localhost named]# ip route del default via 172.31.0.254 dev eth0 proto static metric 100

清除缓存

[root@localhost named]# rndc flush

客户端验证

[17:38:13 root@sz-kx-centos8 ~]# dig www.longxuan.vip @172.31.0.17