How to Setup Master Slave DNS Server on CentOS 6 and RHEL

The DNS ( Domain Name System ) is a distributed system, used for transalate domain names to IP and vice a versa. This article will help you to How to Setup Master Slave DNS Server on CentOS 6 and RHEL Systems.

Network Scenario for this Setup
Master DNS Server IP: 192.168.1.90 ( ns1.tecadmin.net )
Slave  DNS Server IP: 192.168.1.91 ( ns2.tecadmin.net )
Domain Name : demotecadmin.net   ( For Testing Purpose )
Domain IP   : 192.168.1.100  ( For Testing Purpose )
Step 1: Install Required RPMS ( at Master and Slave Both )

Install bind packages at both Master and Slave dns servers using following commands.

# yum install bind bind-chroot
Step 2: Setup Master (NS1) DNS Server

There are two types of configuration files in DNS.

  • One is main dns configuration files named “named.conf”
  • Another type of configuration file are called zone file. Which is individually created for all domains. named.conf keeps an entry for all zone files.
2.1 Configure named.conf using below configuration
# vim /var/named/chroot/etc/named.conf

Content of named.conf:

// /var/named/chroot/etc/named.conf
options {
        listen-on port 53 { 127.0.0.1; 192.168.1.0/24; };
        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";
        allow-query     { localhost; 192.168.1.0/24; };
        recursion yes;

        dnssec-enable yes;
        dnssec-validation yes;
        dnssec-lookaside auto;

        /* Path to ISC DLV key */
        bindkeys-file "/etc/named.iscdlv.key";

        managed-keys-directory "/var/named/dynamic";
};

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

zone "." IN {
        type hint;
        file "named.ca";
};

zone "demotecadmin.net" IN {
        type master;
        file "/var/named/demotecadmin.net.db";
	allow-update { none; };
};

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

[Change red highlighted values as per you network and domain name ]

2.2 Create a zone file for you domain “demotecadmin.net”
# vim /var/named/chroot/var/named/demotecadmin.net.db

Content of zone file:

; Zone file for demotecadmin.net
$TTL 14400
@      86400    IN      SOA     ns1.tecadmin.net. webmaster.tecadmin.net. (
                3215040200      ; serial, todays date+todays
                86400           ; refresh, seconds
                7200            ; retry, seconds
                3600000         ; expire, seconds
                86400 )         ; minimum, seconds

demotecadmin.net. 86400 IN NS ns1.tecadmin.net.
demotecadmin.net. 86400 IN NS ns2.tecadmin.net.
demotecadmin.net. IN A 192.168.1.100
demotecadmin.net. IN MX 0 demotecadmin.net.
mail IN CNAME demotecadmin.net.
www IN CNAME demotecadmin.net.
2.3 Add more domains in dns server

To add more domains in dns, create zone files individually for all domain as above. After that add any entry for all zones in named.conf like below. Change demotecadmin.net with your domain name.

zone "demotecadmin.net" IN {
        type master;
        file "/var/named/demotecadmin.net.db";
	allow-update { none; };
};
Step 2.4: Start named service

Start named (bind) service using following command and setup auto start on system boot.

# /etc/init.d/named restart
# chkconfig named on
Step 3: Setup Slave (NS2) DNS Server

At slave dns server you need to update named.conf file only. All zone files will automatically synced from master dns server. Any changes done on Master will reflect on slave after a specified time interval.

3.1 Configure named.conf using below configuration
# vim /var/named/chroot/etc/named.conf

Content of named.conf

// /var/named/chroot/etc/named.conf
options {
        listen-on port 53 { 127.0.0.1; 192.168.1.0/24; };
        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";
        allow-query     { localhost; 192.168.1.0/24; };
        recursion yes;

        dnssec-enable yes;
        dnssec-validation yes;
        dnssec-lookaside auto;

        /* Path to ISC DLV key */
        bindkeys-file "/etc/named.iscdlv.key";

        managed-keys-directory "/var/named/dynamic";
};

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

zone "." IN {
        type hint;
        file "named.ca";
};

zone "demotecadmin.net" IN {
	type slave;
        file "slaves/demotecadmin.net.db";
	masters { 192.168.1.90; };
};

include "/etc/named.rfc1912.zones";
Step 3.2: Start named Service

Start named (bind) service using below command.

# /etc/init.d/named restart
# chkconfig named on

After restarting named service, Check zone files on slave dns server at /var/named/chroot/var/named/slaves/.

Step 4: Finally Test Your DNS Setup

Query to your Master and Slave DNS Server directly using following commands, You will get the same resonse from both servers.
Syntax: nslookup <domainname.com> <dns server name/ip>

Query to Master DNS Server:

# nslookup demotecadmin.net 192.168.1.90

Server:         192.168.1.90
Address:        192.168.1.90#53

Name:   demotecadmin.net
Address: 192.168.1.100

Query to Slave DNS Server:

# nslookup demotecadmin.net 192.168.1.91

Server:         192.168.1.91
Address:        192.168.1.91#53

Name:   demotecadmin.net
Address: 192.168.1.100

Above outputs is showing that dns server has successfully resolved domain demotecadmin.net from master and slave dns servers.

Read more about dns servers http://en.wikipedia.org/wiki/Name_server

Rahul

Founder of TecAdmin.net. I love to work with Linux and other open source application. Also I like to share knowledge with my friends and other Linux users. Follow me on Twitter, Add me on Google+ or Like Facebook page.

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