How To Configure DNS (BIND) Server On CentOS 8 / RHEL 8

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Configure DNS (BIND) Server On CentOS 8
Configure DNS (BIND) Server On CentOS 8

The Domain Name System (DNS) is a hierarchical distributed naming system for computers, services, or any resource connected to the internet or a private network. It associates various information with domain names assigned to each of the participating entities.

Most importantly, it translates domain names meaningful to humans into the numerical identifiers associated with networking equipment for the purpose of locating and addressing these devices worldwide.

This guide will help you to set up DNS server on CentOS 8 / RHEL 8.

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Assumptions

Host Name: ns1.itzgeek.local

IP Address: 192.168.0.10

Install DNS Server

BIND stands for Berkeley Internet Name Domain, a software that provides an ability to perform name to ip conversion.

yum -y install bind bind-utils

Configure DNS Server

BIND’s main configuration file is /etc/named.conf. We will use this file to configure the DNS server and define the DNS zone.

By default, BIND listens on the localhost. So, we will configure DNS servers to listen on all network interfaces or a particular interface.

Edit the /etc/named.conf file.

vi /etc/named.conf

Comment out the following line. This will enable BIND to listen to system network interfaces other than the localhost.

Listen on all IP address:

//listen-on port 53 { 127.0.0.1; };
//listen-on-v6 port 53 { ::1; };

Listen on particular IP address:

listen-on port 53 { 127.0.0.1; 192.168.0.10; };

Add your network in the following line. I’ve added 192.168.0.0/24 to allow clients from 192.168.0.0/24 network to query the DNS server for the name to ip translation.

allow-query     { localhost;192.168.0.0/24; };

Create Zones

Edit /etc/named.conf file.

vi /etc/named.conf

Forward Zone

The following is the forward zone entry in named.conf file, written for the itzgeek.local domain.

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zone "itzgeek.local" IN { // Domain Name
           
           type master;  // Master DNS Server

           file "itzgeek.local.db";  // Zone File (/var/named/)

           allow-update { none; };  // Since master DNS, it is none

};

itzgeek.local – Domain name
master – Primary DNS
itzgeek.local.db – Forward lookup file
allow-update – Since this is the master DNS, it should be none

Reverse Zone

The following is the reverse zone entry in the named.conf file.

zone "0.168.192.in-addr.arpa" IN { // Reverse Zone Name, should match with network in reverse order
             
             type master;  // Master DNS Server
             
             file "192.168.0.db";  // Zone File (/var/named/) 
             
             allow-update { none; }; // Since master DNS, it is none
 
};

0.168.192.in-addr.arpa – Reverse lookup name
master – Primary DNS
192.168.0.db – Reverse lookup file
allow-update – Since this is the master DNS, it should be none

Create zone files

Now, it’s time to create a lookup file for a created zone. By default, zone lookup files are placed under /var/named directory. Create a zone file called itzgeek.local.db for the forward lookup under /var/named directory.

All domain names should end with a dot (.).

Forward Zone

There are some special keywords for Zone Files

Create a file.

vi /var/named/itzgeek.local.db

A – A record
NS – Name Server
MX – Mail for Exchange
CNAME – Canonical Name

$TTL 86400
@   IN  SOA     ns1.itzgeek.local. root.itzgeek.local. (
                                              3           ;Serial
                                              3600        ;Refresh
                                              1800        ;Retry
                                              604800      ;Expire
                                              86400       ;Minimum TTL
)

;Name Server Information
@       IN  NS      ns1.itzgeek.local.

;IP address of Name Server
ns1       IN  A       192.168.0.10

;Mail exchanger
itzgeek.local. IN  MX 10   mail.itzgeek.local.

;A - Record HostName To Ip Address
www     IN  A       192.168.0.100
mail    IN  A       192.168.0.150

;CNAME record
ftp     IN CNAME        www.itgeek.local.

Whenever you update the zone files for the DNS record update, do not forget to increment the serial.

Reverse Zone

Create a zone file called 192.168.0.db for the reverse zone under /var/named directory, create a reverse pointer to the above forward zone entries.

vi /var/named/192.168.0.db

PTR – Pointer
SOA – Start of Authority

$TTL 86400
@   IN  SOA     ns1.itzgeek.local. root.itzgeek.local. (
                                       3           ;Serial
                                       3600        ;Refresh
                                       1800        ;Retry
                                       604800      ;Expire
                                       86400       ;Minimum TTL
)

;Name Server Information
@         IN      NS         ns1.itzgeek.local.

;Reverse lookup for Name Server
10        IN  PTR     ns1.itzgeek.local.

;PTR Record IP address to HostName
100      IN  PTR     www.itzgeek.local.
150      IN  PTR     mail.itzgeek.local.

Whenever you update the zone files for the DNS record update, do not forget to increment the serial.

Validate DNS Server Configuration

Use named-checkconf command to validate the configuration file.

named-checkconf /etc/named.conf

If you don’t see any error, then you are good to go.

Validate the forward zone file you have created with the below command.

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named-checkzone itzgeek.local /var/named/itzgeek.local.db

itzgeek.localDomain Name

/var/named/itzgeek.local.dbPath to a zone file

Output:

zone itzgeek.local/IN: loaded serial 3
OK
The serial number mentioned in the output should match with the serial number in the zone files.

Perform the same for the reverse zone as well.

named-checkzone 0.168.192.in-addr.arpa /var/named/192.168.0.db

Output:

zone 0.168.192.in-addr.arpa/IN: loaded serial 3
OK

Start DNS Service

Once you validate DNS configurations, restart bind service.

systemctl restart named

Enable it on system startup.

systemctl enable named

DNS Record Update

Whenever you change a DNS record, do not forget to change the serial number in the zone file and reload the zone.

Change itzgeek.local & 0.168.192.in-addr.arpa with your zone names.

### Forward Zone ###

rndc reload itzgeek.local

### Reverse Zone ###

rndc reload 0.168.192.in-addr.arpa

Firewall

Add a firewall rule to allow DNS queries from client machines.

firewall-cmd --permanent --add-port=53/udp

firewall-cmd --reload

Verify DNS Server

Visit any client machine and add a DNS server’s ip address in /etc/resolv.conf if Network Manager does not manage the network.

nameserver 192.168.0.10

If Network Manager manages the networking then place the following entry in /etc/sysconfig/network-scripts/ifcfg-eXX file.

DNS1=192.168.0.10

Restart network service.

service network restart

OR

systemctl restart NetworkManager

Use the following command to verify the forward lookup, where the DNS server gives 192.168.0.100 as ip for www.itzgeek.local.

dig www.itzgeek.local

Output:

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; <<>> DiG 9.11.3-1ubuntu1.7-Ubuntu <<>> www.itzgeek.local
;; global options: +cmd
;; Got answer:
;; WARNING: .local is reserved for Multicast DNS
;; You are currently testing what happens when an mDNS query is leaked to DNS
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 42679
;; flags: qr aa rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 1, ADDITIONAL: 2

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
; COOKIE: 99d94df91828bc8e957709ec5e13f9cd0c242970a9488a91 (good)
;; QUESTION SECTION:
;www.itzgeek.local.             IN      A

;; ANSWER SECTION:
www.itzgeek.local.      86400   IN      A       192.168.0.100

;; AUTHORITY SECTION:
itzgeek.local.          86400   IN      NS      ns1.itzgeek.local.

;; ADDITIONAL SECTION:
ns1.itzgeek.local.      86400   IN      A       192.168.0.10

;; Query time: 0 msec
;; SERVER: 192.168.0.10#53(192.168.0.10)
;; WHEN: Tue Jan 07 08:53:56 IST 2020
;; MSG SIZE  rcvd: 124
Install bind-utils package to get nslookup or dig command.

Confirm the reverse lookup, where the DNS server gives www.itzgeek.local as a name for 192.168.0.100. It is now confirmed that both forward and reverse lookups are working fine.

dig -x 192.168.0.100

Output:

; <<>> DiG 9.11.3-1ubuntu1.7-Ubuntu <<>> -x 192.168.0.100
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 43305
;; flags: qr aa rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 1, ADDITIONAL: 2

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
; COOKIE: d36aa24edb88f8951b3fbf8c5e13fa2cbf0e3ed754a00eee (good)
;; QUESTION SECTION:
;100.0.168.192.in-addr.arpa.    IN      PTR

;; ANSWER SECTION:
100.0.168.192.in-addr.arpa. 86400 IN    PTR     www.itzgeek.local.

;; AUTHORITY SECTION:
0.168.192.in-addr.arpa. 86400   IN      NS      ns1.itzgeek.local.

;; ADDITIONAL SECTION:
ns1.itzgeek.local.      86400   IN      A       192.168.0.10

;; Query time: 0 msec
;; SERVER: 192.168.0.10#53(192.168.0.10)
;; WHEN: Tue Jan 07 08:55:30 IST 2020
;; MSG SIZE  rcvd: 148

Conclusion

That’s All. You have successfully installed BIND on CentOS 8 / RHEL 8 as the master server. In our next article, we will see how to configure a slave DNS server on CentOS 8 / RHEL 8.

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