DNS domain name system is a service of Internet. As a distributed database which maps domain name and IP address, it can make people access the Internet more easily. DNS uses TCP and UDP port 53
 
 

DNS server master-slave replication, subdomain authorization
Main server: 10.120.123.13
Slave server: 10.120.123.250
Sub server: 10.120.123.251
 
 
Master configuration file of slave server / etc/named.conf

options {
        listen-on port 53 { 10.120.123.250; };  //Define listening port and listening ip
        //Listen-on-v6 port 53 {:: 1;}; / / disable IPv6 query
        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     { any; };

        recursion yes;  //Allow recursion

        dnssec-enable no;  //Turn off DNS Security related
        dnssec-validation no;  //Turn off DNS Security related

        bindkeys-file "/etc/named.iscdlv.key";
        managed-keys-directory "/var/named/dynamic";
        pid-file "/run/named/named.pid";
        session-keyfile "/run/named/session.key";
};

logging {                             //Log related configuration
        channel default_debug {
                file "data/named.run";
                severity dynamic;
        };
};

zone "." IN {                        //Define root area
        type hint;
        file "named.ca";
};

include "/etc/named.rfc1912.zones";
include "/etc/named.root.key";

Resolve the library file from the server definition area / etc/named.rfc1912.zones

zone "test.com" IN {
        type slave;     //Define service type slave
        file "slaves/test.com.zone"; 
        masters { 10.120.123.13; };   //Define primary server address
        masterfile-format text;       //Define the format to solve the server area file disorder
};

zone "123.120.10.in-addr.arpa" IN {
        type slave;     //Define service type slave
        file "slaves/10.120.123.zone";   
        masters { 10.120.123.13; };      //Define primary server address
        masterfile-format text;         //Define the format to solve the server area file disorder
};

Main server region resolution library file (/ var/named/test.com.zone): add NS record

$TTL 3600
$ORIGIN test.com.
@       IN      SOA     ns1.test.com.   dnsadmin.test.com. (
        2019010818
        1H
        10M
        3D
        1D )
        IN      NS      ns1
        IN      NS      ns2   //from server
        IN      MX   10 mx1
        IN      MX   20 mx2
ns1     IN      A       10.120.123.13
ns2     IN      A       10.120.123.250   //from server
mx1     IN      A       10.120.123.252
mx2     IN      A       10.120.123.253
www     IN      A       10.120.123.254
web     IN      CNAME   www
ops     IN      NS      ns1.ops         //Subdomain authorization
ns1.ops IN      A       10.120.123.251

$TTL 3600
$ORIGIN 123.120.10.in-addr.arpa.
@       IN      SOA     ns1.test.com.  nsadmin.test.com. (
        2019010802
        1H
        10M
        3D
        12H )
        IN      NS      ns1.test.com.
        IN      NS      ns2.test.com. //from server
13      IN      PTR     ns1.test.com.
250     IN      PTR     ns2.test.com. //from server
252     IN      PTR     mx1.test.com.
253     IN      PTR     mx2.test.com.
254     IN      PTR     www.test.com.

Sub domain region resolution library file (/ var/named/ops.test.com.zone)

$TTL 3600 
$ORIGIN ops.test.com.
@       IN      SOA     ns1.ops.test.com.     nsadmin.ops.test.com. (
                2019022401
                1H
                10M
                1D
                2H )
        IN      NS      ns1
ns1     IN      A       10.120.123.251
www     IN      A       10.120.123.251

Master server reloads master configuration

rndc reload

Start service from server

systemctl restart  named.service

Test from server

Full zone transfer
dig -t axfr test.com @10.120.123.13
 Forward analysis
dig -t A www.test.com @10.120.123.250
 Backward analysis
dig -x 10.120.123.13 @10.120.123.250

Subdomain testing

dig www.ops.test.com @10.120.123.13   //main
dig www.ops.test.com @10.120.123.250 //from
dig www.ops.test.com @10.120.123.251 //son