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 dnsutilsCopy code

Configuring BIND on the primary instance

1. Edit the name.conf.local file:

   cd /etc/bindnano named.conf.localeCopy code

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;        };Copy code

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.mlCopy code

4. Paste the following:

   ;; BIND data file for local loopback interface;$TTL    10800scw-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       51.15.242.21ns1     86400   IN      AAAA    2001:bc8:4400:2c00::14:229ns2     86400   IN      A       51.15.250.21ns2     86400   IN      AAAA    2001:bc8:4400:2c00::2c:1fwww     86400   IN      A       51.15.242.21www     86400   IN      AAAA    2001:bc8:4400:2c00::14:229Copy code

Configuring Bind on the secondary instance

1. Edit the name.conf.local file:

   cd /etc/bindnano named.conf.localCopy code

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;  };        };Copy code

3. On the primary machine, restart the service to verify that the zone replication works properly:

service bind9 restartCopy code

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 dateJan 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 dateCopy code

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   51.15.242.21Copy code