What is a DNS Zone?

A DNS Zone if a very important part of the DNS servers, on this post we will learn what is a DNS zone, what it is used for, and a simple way to edit dns zones on cPanel based servers.

What is a DNS Zone and what is it useful for?

DNS Zones are part of the dns server configuration. Each zone is used to store information about your dns records. This information is used by the dns server to serve your dns settings each time an user makes a request.

Example of a DNS Zone

This is an example of a DNS zone I created for this tutorial, it is not real, but it is based on the cPanel DNS zone template that is used on all the cPanel installations.

You will see there is lot of information on this dns zone, such as:

  • Serial number
  • Refresh time
  • Retry time
  • Expire & minimum time

After that you will see the NS records for the current Name Servers used by the DNS server:

nixcp.com.	86400	IN	NS	dns1.nixcp.com.
nixcp.com.	86400	IN	NS	dns2.nixcp.com.

And after that you will see the full list of A, CANME, and TXT records for the “nixcp.com” domain name.
All those records, along with the NS information, are part of the DNS zone. A DNS zone without records is useful for the dns servers, it must contain at least your root domain record (@), and your www record if you use it. On this example based on cPanel dns zone template you will notice extra records like webmail, whm, cpcontacts, cpcalendars, webdisk and others.

[root@server.nixcp.com:~]cat nixcp.com.db 
; cPanel first: (update_time):1485982931 Cpanel::ZoneFile::VERSION:1.3
; Zone file for nixcp.com
$TTL 14400
nixcp.com.	86400	IN	SOA	server.nixcp.com.	my@email.com.	(
						2017020100 ;Serial Number
						3600 ;refresh
						7200 ;retry
						1209600 ;expire
						86400 ;minimum
nixcp.com.	86400	IN	NS	dns1.nixcp.com.
nixcp.com.	86400	IN	NS	dns2.nixcp.com.
nixcp.com.	14400	IN	A
nixcp.com.	14400	IN	MX	0	nixcp.com.
mail	14400	IN	CNAME	nixcp.com.
www	14400	IN	CNAME	nixcp.com.
ftp	14400	IN	A
cpanel	14400	IN	A
webdisk	14400	IN	A
cpcalendars	14400	IN	A
cpcontacts	14400	IN	A
whm	14400	IN	A
webmail	14400	IN	A
autoconfig	14400	IN	A
autodiscover	14400	IN	A
nixcp.com. IN TXT "v=spf1 +a +mx +ip4: -all"

How can I edit a DNS Zone?

On cPanel servers, DNS zones can be edited from this place:

WHM » DNS Functions » Edit DNS Zone

After you make the changes, cPanel will reload your dns zone configuration for your dns server and it will apply the changes for you.

How can I check my DNS record change is responding OK?

You can use tools like DNS propagation, which will help you to determine if your DNS zone modification is propagating OK or not.

DNS changes at zone level are usually faster than Name Server changes, and the new information can be confirmed within just a few minutes after the change.

You can also check your DNS records using tools like ping or dig, for example:

ping nixcp.com

On this output, you will get your nixcp.com server IP. This is useful if you changed your main A record.

[webtech@localhost ~]$ ping nixcp.com
PING nixcp.com ( 56(84) bytes of data.

If you changed other type of record, like a subdomain record, do the same:

ping subdomain.nixcp.com

Using Dig to retrieve dns records information:

[webtech@localhost ~]$ dig A nixcp.com

; <<>> DiG 9.10.4-P6-RedHat-9.10.4-4.P6.fc25 <<>> A nixcp.com
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 47817
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 4, ADDITIONAL: 7

; EDNS: version: 0, flags:; udp: 512
;nixcp.com. IN A

nixcp.com. 1276 IN A

nixcp.com. 82234 IN NS ns4.dnsmadeeasy.com.
nixcp.com. 82234 IN NS ns3.dnsmadeeasy.com.
nixcp.com. 82234 IN NS ns2.dnsmadeeasy.com.
nixcp.com. 82234 IN NS ns0.dnsmadeeasy.com.

ns0.dnsmadeeasy.com. 83712 IN A
ns2.dnsmadeeasy.com. 78014 IN A
ns3.dnsmadeeasy.com. 76793 IN A
ns3.dnsmadeeasy.com. 86358 IN AAAA 2600:1801:3::1
ns4.dnsmadeeasy.com. 83712 IN A
ns4.dnsmadeeasy.com. 196 IN AAAA 2600:1802:4::1

;; Query time: 6 msec
;; WHEN: Fri Apr 28 09:57:58 -03 2017
;; MSG SIZE rcvd: 263

[webtech@localhost ~]$

Further reading:

About the Author: Esteban Borges

Experienced Sr. Linux SysAdmin and Web Technologist, passionate about building tools, automating processes, fixing server issues, troubleshooting, securing and optimizing high traffic websites.