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DNS SERVER CENTOS 6.3

DNS, Domain Name System, translates hostnames or URLs into IP addresses. For example if we type www.unixmen.com in browser, the DNS server translates the domain name into its associated ip address.

Since the IP addresses are hard to remember, DNS servers are used to translate the hostnames like www.unixmen.com to 173.xxx.xx.xxx. So it makes easy to remember the domain names instead of its ip address.

DNS Server Installation in CentOS 6.3

Scenario

Primary(Master) DNS Server Details:

Operating System     : CentOS 6.3 server
Hostname             : masterdns.unixmen.local
IP Address           : 192.168.1.100/24

Secondary(Slave) DNS Server Details:

Operating System     : CentOS 6.3 server
Hostname             : secondarydns.unixmen.local
IP Address           : 192.168.1.101/24

Client Details:

Operating System     : CentOS 6.3 Desktop  
Hostname             : Client.unixmen.local
IP Address           : 192.168.1.102/24

Setup Primary(Master) DNS Server

[root@masterdns ~]# yum install bind* -y

1. Configure DNS Server

Add the lines as shown below in ‘/etc/named.conf’ file

[root@masterdns ~]# vi /etc/named.conf 
//
// named.conf
//
// Provided by Red Hat bind package to configure the ISC BIND named(8) DNS
// server as a caching only nameserver (as a localhost DNS resolver only).
//
// See /usr/share/doc/bind*/sample/ for example named configuration files.
//
options {
listen-on port 53 { 127.0.0.1;

2. Create Zone files

Create forward and reverse zone files which we mentioned in the ‘/etc/named.conf’ file.

2.1 Create Forward Zone

Create forward.unixmen file in the ‘/var/named’ directory.

[root@masterdns ~]# vi /var/named/forward.unixmen
$TTL 86400
@   IN  SOA     masterdns.unixmen.local. root.unixmen.local. (
        2011071001  ;Serial
        3600        ;Refresh
        1800        ;Retry
        604800      ;Expire
        86400       ;Minimum TTL
)
@       IN  NS          masterdns.unixmen.local.
@       IN  NS          secondarydns.unixmen.local.
@       IN  A           192.168.1.100
@       IN  A           192.168.1.101
@       IN  A           192.168.1.102
masterdns       IN  A   192.168.1.100
secondarydns    IN  A   192.168.1.101
client          IN  A   192.168.1.102

2.2 Create Reverse Zone

Create reverse.unixmen file in the ‘/var/named’ directory.

[root@masterdns ~]# vi /var/named/reverse.unixmen 
$TTL 86400
@   IN  SOA     masterdns.unixmen.local. root.unixmen.local. (
        2011071001  ;Serial
        3600        ;Refresh
        1800        ;Retry
        604800      ;Expire
        86400       ;Minimum TTL
)
@       IN  NS          masterdns.unixmen.local.
@       IN  NS          secondarydns.unixmen.local.
@       IN  PTR         unixmen.local.
masterdns       IN  A   192.168.1.100
secondarydns    IN  A   192.168.1.101
client          IN  A   192.168.1.102
100     IN  PTR         masterdns.unixmen.local.
101     IN  PTR         secondarydns.unixmen.local.
102     IN  PTR         client.unixmen.local.

3. Start the DNS service

[root@masterdns ~]# service named start
Starting named:                                            [  OK  ]
[root@masterdns ~]# chkconfig named on

4. Adjust iptables to allow DNS server from outside of the network

Add the lines as shown below in ‘/etc/sysconfig/iptables’ file.

[root@masterdns ~]# vi /etc/sysconfig/iptables
# Firewall configuration written by system-config-firewall
# Manual customization of this file is not recommended.
*filter
:INPUT ACCEPT [0:0]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [0:0]

5. Restart iptables

[root@masterdns ~]# service iptables restart
iptables: Flushing firewall rules:                         [  OK  ]
iptables: Setting chains to policy ACCEPT: filter          [  OK  ]
iptables: Unloading modules:                               [  OK  ]
iptables: Applying firewall rules:                         [  OK  ]

6. Test DNS configuration and zone files for any syntax errors

[root@masterdns ~]# named-checkconf /etc/named.conf 
[root@masterdns ~]# named-checkzone unixmen.local /var/named/forward.unixmen 
zone unixmen.local/IN: loaded serial 2011071001
OK
[root@masterdns ~]# named-checkzone unixmen.local /var/named/reverse.unixmen 
zone unixmen.local/IN: loaded serial 2011071001
OK

7. Test DNS Server

[root@masterdns ~]# dig masterdns.unixmen.local
;  DiG 9.8.2rc1-RedHat-9.8.2-0.10.rc1.el6_3.6  masterdns.unixmen.local
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 49834
;; flags: qr aa rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 2, ADDITIONAL: 1
;; QUESTION SECTION:
;masterdns.unixmen.local.INA
;; ANSWER SECTION:
masterdns.unixmen.local. 86400INA192.168.1.100
;; AUTHORITY SECTION:
unixmen.local.86400INNSsecondarydns.unixmen.local.
unixmen.local.86400INNSmasterdns.unixmen.local.
;; ADDITIONAL SECTION:
secondarydns.unixmen.local. 86400 INA192.168.1.101
;; Query time: 6 msec
;; SERVER: 192.168.1.100#53(192.168.1.100)
;; WHEN: Thu Mar  7 13:07:56 2013
;; MSG SIZE  rcvd: 114

[root@masterdns ~]# nslookup unixmen.local
Server:192.168.1.100
Address:192.168.1.100#53
Name:unixmen.local
Address: 192.168.1.102
Name:unixmen.local
Address: 192.168.1.100
Name:unixmen.local
Address: 192.168.1.101

Now the Primary DNS server is ready to use.

Setup Secondary(Slave) DNS Server

[root@secondarydns ~]# yum install bind* -y

1. Configure Slave DNS Server

Open the main configuration file ‘/etc/named.conf’ and add the lines as shown below.

[root@secondarydns ~]# vi /etc/named.conf 
//
// named.conf
//
// Provided by Red Hat bind package to configure the ISC BIND named(8) DNS
// server as a caching only nameserver (as a localhost DNS resolver only).
//
// See /usr/share/doc/bind*/sample/ for example named configuration files.
//
options {
listen-on port 53 { 127.0.0.1;

2. Start the DNS Service

[root@secondarydns ~]# service named start
Generating /etc/rndc.key:                                  [  OK  ]
Starting named:                                            [  OK  ]
[root@secondarydns ~]# chkconfig named on

Now the forward and reverse zones are automatically replicated from Master DNS server to‘/var/named/slaves/’ in Secondary DNS server.

[root@secondarydns ~]# ls /var/named/slaves/

[root@secondarydns ~]# cat /var/named/slaves/unixmen.fwd 
$ORIGIN .
$TTL 86400; 1 day
unixmen.localIN SOAmasterdns.unixmen.local. root.unixmen.local. (
2011071001 ; serial
3600       ; refresh (1 hour)
1800       ; retry (30 minutes)
604800     ; expire (1 week)
86400      ; minimum (1 day)
)
NS masterdns.unixmen.local.
NS secondarydns.unixmen.local.
A192.168.1.100
A192.168.1.101
A192.168.1.102
$ORIGIN unixmen.local.
clientA192.168.1.102
masterdnsA192.168.1.100
secondarydnsA192.168.1.101

[root@secondarydns ~]# cat /var/named/slaves/unixmen.rev 
$ORIGIN .
$TTL 86400; 1 day
1.168.192.in-addr.arpaIN SOAmasterdns.unixmen.local. root.unixmen.local. (
2011071001 ; serial
3600       ; refresh (1 hour)
1800       ; retry (30 minutes)
604800     ; expire (1 week)
86400      ; minimum (1 day)
)
NS masterdns.unixmen.local.
NS secondarydns.unixmen.local.
PTRunixmen.local.
$ORIGIN 1.168.192.in-addr.arpa.
100PTRmasterdns.unixmen.local.
101PTRsecondarydns.unixmen.local.
102PTRclient.unixmen.local.
clientA192.168.1.102
masterdnsA192.168.1.100
secondarydnsA192.168.1.101

3. Add the DNS Server details to all systems

[root@secondarydns ~]# vi /etc/resolv.conf
# Generated by NetworkManager
search ostechnix.com
nameserver 192.168.1.100
nameserver 192.168.1.101
nameserver 8.8.8.8

4. Test DNS Server

[root@secondarydns ~]# dig masterdns.unixmen.local
;  DiG 9.8.2rc1-RedHat-9.8.2-0.10.rc1.el6_3.6  masterdns.unixmen.local
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 21487
;; flags: qr aa rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 2, ADDITIONAL: 1
;; QUESTION SECTION:
;masterdns.unixmen.local.INA
;; ANSWER SECTION:
masterdns.unixmen.local. 86400INA192.168.1.100
;; AUTHORITY SECTION:
unixmen.local.86400INNSmasterdns.unixmen.local.
unixmen.local.86400INNSsecondarydns.unixmen.local.
;; ADDITIONAL SECTION:
secondarydns.unixmen.local. 86400 INA192.168.1.101
;; Query time: 15 msec
;; SERVER: 192.168.1.100#53(192.168.1.100)
;; WHEN: Thu Mar  7 13:27:57 2013
;; MSG SIZE  rcvd: 114

[root@secondarydns ~]# dig secondarydns.unixmen.local
;  DiG 9.8.2rc1-RedHat-9.8.2-0.10.rc1.el6_3.6  secondarydns.unixmen.local
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 20958
;; flags: qr aa rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 2, ADDITIONAL: 1
;; QUESTION SECTION:
;secondarydns.unixmen.local.INA
;; ANSWER SECTION:
secondarydns.unixmen.local. 86400 INA192.168.1.101
;; AUTHORITY SECTION:
unixmen.local.86400INNSmasterdns.unixmen.local.
unixmen.local.86400INNSsecondarydns.unixmen.local.
;; ADDITIONAL SECTION:
masterdns.unixmen.local. 86400INA192.168.1.100
;; Query time: 4 msec
;; SERVER: 192.168.1.100#53(192.168.1.100)
;; WHEN: Thu Mar  7 13:31:53 2013
;; MSG SIZE  rcvd: 114

[root@secondarydns ~]# nslookup unixmen.local
Server:192.168.1.100
Address:192.168.1.100#53
Name:unixmen.local
Address: 192.168.1.101
Name:unixmen.local
Address: 192.168.1.102
Name:unixmen.local
Address: 192.168.1.100

Client Side Configuration

Add the DNS server details in ‘/etc/resolv.conf’ file in all client systems

[root@client unixmen]# vi /etc/resolv.conf
# Generated by NetworkManager
search unixmen.local
nameserver 192.168.1.100
nameserver 192.168.1.101
nameserver 8.8.8.8

Test DNS Server

[root@client unixmen]# dig masterdns.unixmen.local
;  DiG 9.8.2rc1-RedHat-9.8.2-0.10.rc1.el6  masterdns.unixmen.local
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 19496
;; flags: qr aa rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 2, ADDITIONAL: 1
;; QUESTION SECTION:
;masterdns.unixmen.local.INA
;; ANSWER SECTION:
masterdns.unixmen.local. 86400INA192.168.1.100
;; AUTHORITY SECTION:
unixmen.local.86400INNSmasterdns.unixmen.local.
unixmen.local.86400INNSsecondarydns.unixmen.local.
;; ADDITIONAL SECTION:
secondarydns.unixmen.local. 86400 INA192.168.1.101
;; Query time: 30 msec
;; SERVER: 192.168.1.100#53(192.168.1.100)
;; WHEN: Thu Mar  7 13:47:55 2013
;; MSG SIZE  rcvd: 114

[root@client unixmen]# dig secondarydns.unixmen.local
;  DiG 9.8.2rc1-RedHat-9.8.2-0.10.rc1.el6  secondarydns.unixmen.local
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 14852
;; flags: qr aa rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 2, ADDITIONAL: 1
;; QUESTION SECTION:
;secondarydns.unixmen.local.INA
;; ANSWER SECTION:
secondarydns.unixmen.local. 86400 INA192.168.1.101
;; AUTHORITY SECTION:
unixmen.local.86400INNSsecondarydns.unixmen.local.
unixmen.local.86400INNSmasterdns.unixmen.local.
;; ADDITIONAL SECTION:
masterdns.unixmen.local. 86400INA192.168.1.100
;; Query time: 8 msec
;; SERVER: 192.168.1.100#53(192.168.1.100)
;; WHEN: Thu Mar  7 13:48:38 2013
;; MSG SIZE  rcvd: 114

[root@client unixmen]# dig client.unixmen.local
;  DiG 9.8.2rc1-RedHat-9.8.2-0.10.rc1.el6  client.unixmen.local
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 14604
;; flags: qr aa rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 2, ADDITIONAL: 2
;; QUESTION SECTION:
;client.unixmen.local.INA
;; ANSWER SECTION:
client.unixmen.local.86400INA192.168.1.102
;; AUTHORITY SECTION:
unixmen.local.86400INNSmasterdns.unixmen.local.
unixmen.local.86400INNSsecondarydns.unixmen.local.
;; ADDITIONAL SECTION:
masterdns.unixmen.local. 86400INA192.168.1.100
secondarydns.unixmen.local. 86400 INA192.168.1.101
;; Query time: 5 msec
;; SERVER: 192.168.1.100#53(192.168.1.100)
;; WHEN: Thu Mar  7 13:49:11 2013
;; MSG SIZE  rcvd: 137

[root@client unixmen]# nslookup unixmen.local
Server:192.168.1.100
Address:192.168.1.100#53
Name:unixmen.local
Address: 192.168.1.102
Name:unixmen.local
Address: 192.168.1.100
Name:unixmen.local
Address: 192.168.1.101

Thats all about it. Now the primary and secondary DNS servers are ready. Enjoy.

Source : www.tkjclub.net

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