The DNS Server stands for Domain Naming System. The name servers are dynamically updated with the DNS server. In this tutorial we will describe about the given guide in a step by step manner on Enterprise Linux.

Host File

  • The host file provides resolution of hostname to IP addresses.
  • Only resolve names provide in the local host file.
  • Cannot be used as a centralized database.
  • The hostname and IP address mapping is given in /etc/hosts

Hostname Resolution

Hostname-Resolution

Host File Configuration

Edit the configuration file

 vi /etc/hosts

Add the entries required

127.0.0.1 localhost.localdomain localhost
192.168.0.253 dns.example.com dns
192.168.0.1 client1.example.com client1
192.168.0.2 client2.example.com client2

:wq!

Domain Name System (DNS)

  • The Domain Name System (DNS) is a hierarchical naming system where each level of name is separated by a “.”.
  • Resolves user friendly domain names into computer friendly IP addresses.
  • Also resolves IP addresses into domain names.
  • Provides a centralized database for resolution.

Dynamic DNS

  • Dynamic DDNS
  • DNS is configured with DHCP in such a way that ip & FQDN automatically gets updated over DNS forward & Reverse zone files.
  • Zone journal files are automatically create in Database of DNS with extensions .jnl

DNS Namespace

DNS-Namespace

How DNS works ?

How-DNS-Works

Zone

Zone is a storage database which contains all the records.There are two zones:

Forward Lookup Zone
  • Used for resolving hostnames to IP address.
  • It maintains host to IP address mapping information.
 Reverse Lookup Zone
  • Used for resolving IP address to hostnames.
  • It maintains IP address to hostname mapping information.

Records

SOA Record
  • Start of Authority
  • It is the first record in any zone file.
NS Record
  • Name Server
  • Identifies the DNS server for each zone.
A Record
  • Address
  • Maps a hostname to an IP address.
CNAME Record
  • Canonical Name (Alias)
  • Maps an alias name to a hostname
PTR Record
  • Pointer
  • Maps an IP address to a hostname.
MX Record
  • Mail Exchange
  • Maps a domain name to a mail server.

DNS Quick Snapshots

Packages
  • bind
  • caching
  • dhcp*
Port number
  • 53 for DNS
  • 67, 68 for DHCP
Configuration files
  • /etc/named.conf
Daemon
  • named

DNS Configuration

Step-1 (Installing DNS)
 dnf install bind* caching* dhcp* vim
Step-2 (Configuration of named.rfc1912.zones)

Edit the configuration file

 vim /etc/named.conf

To add the options

controls {
inet 127.0.0.1 port 953
allow {127.0.0.1;} keys {"rndckey";};
};
zone "example.com" IN {
type master;
file “example.for";
allow?update { key rndckey; } ;
};
zone "0.168.192.in?addr.arpa" IN {
type master;
file “example.rev";
allow-update { key rndckey; } ;
};

:wq

Step-3 (Configuration – Forward Lookup Zone)

Copy the forward lookup zone file

 cd /var/named/chroot/var/named/
 cp -arv localhost.zone example.for

Note: The file has to be copied with the permission

Configuration – Reverse Lookup Zone

Edit the file example.rev

 vim example.rev

To add the options

TTL 86400
@ IN SOA @ root (
42 ; serial (d. adams)
3H ; refresh
15M ; retry
1W ; expire
1D) ; minimum
IN NS @
IN A 192.168.0.253
client1 IN A 192.168.0.1
client2 IN A 192.168.0.2
Step-4 (Configuration – Reverse Lookup Zone)

Copy the reverse lookup zone file

 cd /var/named/chroot/var/named/
 cp -arv named.local example.rev

Note: The file has to be copied with the permission

Configuration – Reverse Lookup Zone

Edit the file example.rev

 vim example.rev

To add the options

TTL 86400
@ IN SOA dns.example.com. root.example.com.(
1997022700 ; Serial
28800 ; Refresh
14400 ; Retry
3600000 ; Expire
86400) ; Minimum
IN NS dns.example.com.
253 IN PTR dns.
1 IN PTR client1.
2 IN PTR client2
Step-5 (Configuration of DNS Server IP Address)

Edit the configuration file

 vim /etc/resolv.conf

Add the following options

nameserver 192.168.0.253
Step-6 (Restart the Services)

Restart the DNS services

 systemctl restart named
Step-7 (Configuration of DNS Server IP Address)

Edit the configuration file

 vim /etc/resolv.conf

Add the following options

nameserver 192.168.0.253
Step-8 (Checking the Configuration)

Checking forward lookup

 dig dns.example.com
 dig client2.example.com

Checking reverse lookup

 dig vx 192.168.0.2
 dig vx 192.168.0.253

Mount the remote file system

 ping dns.example.com
 ping client2.example.com
Step-9 (Configuration of named.rfc1912.zones)

Edit the configuration file

 vim /etc/dhcpd.conf

To add the options

include "/etc/rndc.key";
ddns-domain “example.com";
ddns-update-style interim;
ddns-rev-domain "0.168.192.in-addr.arpa";
ddns-updates on; allow Dynamic DNS
authoritative;
master server for this domain
 Allow only the DHCP server to update DNS
ignore client-updates;
allow unknown-clients;zone 0.168.192.in-addr.arpa.
{
primary 192.168.0.252;
key "rndckey";
}
zone techbrown.com. {
primary 192.168.0.252;
key "rndckey";
}
range 192.168.0.20 192.168.0.59;

:wq(save and quit)

Step-10 (Restart the Services)

Restart the DHCP services

 systemctl restart dhcpd
Step-11 (Configuration file for ddclient)
 dnf install ddclient*
 vim /etc/ddclient.conf
pid=/var/run/ddclient.pid
protocol=easydns
use=if, if=eth0
server=dns.example.com

 dhclient -r
 dhclient
Step-12 (Check the updates)

Now go to forward/reverse zone file and check the updates

Congratulations now you have configured Dynamic DNS server on Enterprise Linux.