Implementing a DNS server using BIND

• apps
• dns
• bind

DNS (Domain Name System) is a service that translates the IP address of computers connected to the Internet into human-readable domain names & vice-versa. In an environment with a limited amount of Linux machines, it is possible to use the /etc/hosts file for associating an IP address to a DNS name but when you have a large infrastructure with lots of systems/resources, /etc/hosts becomes easily cumbersome.

BIND or Berkeley Internet Name Domain, is an open source software that implements DNS protocols for Internet. In this tutorial, we need a DNS server machine & a client machine for testing.

Installing BIND

Install BIND and its related tools.

apt-get install bind9 bind9utils bind9-doc dnsutils
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Configuring BIND on the primary instance

1. Edit the name.conf.local file:

   cd /etc/bind
   nano named.conf.locale
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2. Paste the following. Make sure to edit the domain name and the IP address of the secondary machine.

   //
   // Do any local configuration here
   //
   
   // Consider adding the 1918 zones here, if they are not used in your
   // organization
   //include "/etc/bind/zones.rfc1918";
   
   zone "scw-domain.ml" IN {
                   type master;
                   file "/etc/bind/db.scw-domain.ml";
                   allow-update { 51.15.250.21; };
                   allow-transfer { 51.15.250.21; };
                   notify yes;
           };
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3. Create your zone file. A zone file must contain at least an SOA, a NS and a A record or CNAME.

   nano db.scw-domain.ml
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4. Paste the following:

   ;
   ; BIND data file for local loopback interface
   ;
   $TTL    10800
   scw-domain.ml.  IN      SOA     ns1.scw-domain.ml. admin.scw-domain.ml. (
                           2018120615      ; Serial
                             10800         ; Refresh
                             3600          ; Retry
                           2419200         ; Expire
                           604800 )       ; Negative Cache TTL
   ;
   
   ; Nameserver
   
   scw-domain.ml.  IN      NS      ns1.scw-domain.ml.
   scw-domain.ml.  IN      NS      ns2.scw-domain.ml.
   ns1     86400   IN      A       51.15.242.21
   ns1     86400   IN      AAAA    2001:bc8:4400:2c00::14:229
   ns2     86400   IN      A       51.15.250.21
   ns2     86400   IN      AAAA    2001:bc8:4400:2c00::2c:1f
   www     86400   IN      A       51.15.242.21
   www     86400   IN      AAAA    2001:bc8:4400:2c00::14:229
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Configuring Bind on the secondary instance

1. Edit the name.conf.local file:

   cd /etc/bind
   nano named.conf.local
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2. Paste the following:

   //
   // Do any local configuration here
   //
   
   // Consider adding the 1918 zones here, if they are not used in your
   // organization
   //include "/etc/bind/zones.rfc1918";
   zone "scw-domain.ml" IN {
                   type slave;
                   file "/etc/bind/db.scw-domain.ml";
                   masters { 51.15.242.21; };
                   allow-transfer { none; };
                   allow-notify { 127.0.0.1; 51.15.242.21; 51.15.250.21; 2001:bc8:4400:2c00::14:229;  };
           };
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3. On the primary machine, restart the service to verify that the zone replication works properly:

service bind9 restart
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The following output should be displayed in the syslog file of the secondary machine

tail /var/log/syslog

Jan 11 17:24:22 bind-client named[11492]: client @0x7fa0d00c7260 51.15.242.21#42782: received notify for zone 'scw-domain.ml'
Jan 11 17:24:22 bind-client named[11492]: zone scw-domain.ml/IN: notify from 51.15.242.21#42782: zone is up to date
Jan 11 17:24:22 bind-client named[11492]: client @0x7fa0d003b900 2001:bc8:4400:2c00::14:229#53121: received notify for zone 'scw-domain.ml'
Jan 11 17:24:22 bind-client named[11492]: zone scw-domain.ml/IN: notify from 2001:bc8:4400:2c00::14:229#53121: zone is up to date
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You can try to resolve hostnames on both servers by typing dig www.scw-domain.ml @ns1.scw-domain.ml & dig www.scw-domain.ml @ns2.scw-domain.ml

You should see in the answer section the following:

;; ANSWER SECTION:
www.scw-domain.ml.  86400   IN  A   51.15.242.21
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