- DNS = Domain Naming Service (or) Domain Name System DNS will resolve the host name for the particular IP address.
- WINS provides only netbios to IP but not from IP to netbios
- DNS & WINS reduces the broadcast
- Host file located in /etc/hosts
=> Zone
- Storage database which contains all the records.
1. Forward lookup Zone
- Used for resolving hostnames to IP
- Maintains host to IP mapping info
2. Revers lookup Zone
- Used to resolve IP to hostname
- Maintains IP to host mapping info
=> Records
1. PTR Record /Reverse lookup Zone
- Maps IP to Hostname
2. SOA Record /Forward lookup Zone
- First Record in any zone file
- Primary and Start Of Authority
3. NS Record /Forward lookup Zone
- Name server
- Identifies the DNS servers for each zone
4. MX Record /Forward lookup Zone
- Maps domain name to a mail server
- Mail Exchange
5. A Record (Address Record) /Forward lookup Zone
- Maps hostname to an IP address
- Client Side
6. SRV Record /Forward lookup Zone
- Service Record
7. CNAME Record (Canonical Name)
- Maps an alias name to a hostname
=> Packages
- bind*
- caching-nameserver-*.rpm
=> Port number
- 53
=> Configuration file
- /etc/named.caching-nameserve.conf
- /etc/named.rtc1912.zones
=> Daemon/Service
- named
Primary(Master) DNS Server Details:
Operating System : CentOS 6.5 server
Hostname : masterdns.rhce.local
IP Address : 192.168.1.100/24[Installation on Server Side]
Secondary(Slave) DNS Server Details:
Operating System : CentOS 6.5 server
Hostname : secondarydns.rhce.local
IP Address : 192.168.1.101/24
Client Details:
Operating System : CentOS 6.5 Desktop
Hostname : Client.rhce.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@master ~]# 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; 192.168.1.100; }; ### Master DNS IP ###
listen-on-v6 port 53 { ::1; };
directory "/var/named";
dump-file "/var/named/data/cache_dump.db";
statistics-file "/var/named/data/named_stats.txt";
memstatistics-file "/var/named/data/named_mem_stats.txt";
allow-query { localhost; 192.168.1.0/24; }; ### IP Range ###
allow-transfer{ localhost; 192.168.1.101; }; ### Slave DNS IP ###
recursion yes;
dnssec-enable yes;
dnssec-validation yes;
dnssec-lookaside auto;
/* Path to ISC DLV key */
bindkeys-file "/etc/named.iscdlv.key";
managed-keys-directory "/var/named/dynamic";
};
logging {
channel default_debug {
file "data/named.run";
severity dynamic;
};
};
zone "." IN {
type hint;
file "named.ca";
};
zone"rhce.local" IN {
type master;
file "forward.rhce";
allow-update { none; };
};
zone"1.168.192.in-addr.arpa" IN {
type master;
file "reverse.rhce";
allow-update { none; };
};
include "/etc/named.rfc1912.zones";
include "/etc/named.root.key";
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.rhce file in the ‘/var/named’ directory.
[root@master ~]# vi /var/named/forward.rhce
$TTL 86400
@ IN SOA master.rhce.local. root.rhce.local. (
2011071001 ;Serial
3600 ;Refresh
1800 ;Retry
604800 ;Expire
86400 ;Minimum TTL
)
@ IN NS master.rhce.local.
@ IN NS secondary.rhce.local.
@ IN A 192.168.1.100
@ IN A 192.168.1.101
@ IN A 192.168.1.102
master IN A 192.168.1.100
secondary IN A 192.168.1.101
client IN A 192.168.1.102
2.2 Create Reverse Zone
Create reverse.rhce file in the ‘/var/named’ directory.
[root@master ~]# vi /var/named/reverse.rhce
$TTL 86400
@ IN SOA master.rhce.local. root.rhce.local. (
2011071001 ;Serial
3600 ;Refresh
1800 ;Retry
604800 ;Expire
86400 ;Minimum TTL
)
@ IN NS master.rhce.local.
@ IN NS secondary.rhce.local.
@ IN PTR rhce.local.
master IN A 192.168.1.100
secondary IN A 192.168.1.101
client IN A 192.168.1.102
100 IN PTR master.rhce.local.
101 IN PTR secondary.rhce.local.
102 IN PTR client.rhce.local.
3. Start the DNS service
[root@master ~]# service named start
Starting named: [ OK ]
[root@master ~]# 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@master ~]# 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]
-A INPUT -p udp -m state --state NEW --dport 53 -j ACCEPT
-A INPUT -p tcp -m state --state NEW --dport 53 -j ACCEPT
-A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
-A INPUT -p icmp -j ACCEPT
-A INPUT -i lo -j ACCEPT
-A INPUT -m state --state NEW -m tcp -p tcp --dport 22 -j ACCEPT
-A INPUT -j REJECT --reject-with icmp-host-prohibited
-A FORWARD -j REJECT --reject-with icmp-host-prohibited
COMMIT
5. Restart iptables
[root@master ~]# 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@master ~]# named-checkconf /etc/named.conf
[root@master ~]# named-checkzone rhce.local /var/named/forward.rhce
zone rhce.local/IN: loaded serial 2011071001
OK
[root@master ~]# named-checkzone rhce.local /var/named/reverse.rhce
zone rhce.local/IN: loaded serial 2011071001
OK
7. Test DNS Server
[root@master ~]# dig master.rhce.local
; <<>> DiG 9.8.2rc1-RedHat-9.8.2-0.10.rc1.el6_3.6 <<>> master.rhce.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:
;master.rhce.local.INA
;; ANSWER SECTION:
master.rhce.local. 86400INA192.168.1.100
;; AUTHORITY SECTION:
rhce.local.86400INNSsecondary.rhce.local.
rhce.local.86400INNSmaster.rhce.local.
;; ADDITIONAL SECTION:
secondary.rhce.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@master ~]# nslookup rhce.local
Server:192.168.1.100
Address:192.168.1.100#53
Name:rhce.local
Address: 192.168.1.102
Name:rhce.local
Address: 192.168.1.100
Name:rhce.local
Address: 192.168.1.101
Now the Primary DNS server is ready to use.
Setup Secondary(Slave) DNS Server
[root@secondary ~]# 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@secondary ~]# 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; 192.168.1.101; };
listen-on-v6 port 53 { ::1; };
directory "/var/named";
dump-file "/var/named/data/cache_dump.db";
statistics-file "/var/named/data/named_stats.txt";
memstatistics-file "/var/named/data/named_mem_stats.txt";
allow-query { localhost; 192.168.1.0/24; };
recursion yes;
dnssec-enable yes;
dnssec-validation yes;
dnssec-lookaside auto;
/* Path to ISC DLV key */
bindkeys-file "/etc/named.iscdlv.key";
managed-keys-directory "/var/named/dynamic";
};
logging {
channel default_debug {
file "data/named.run";
severity dynamic;
};
};
zone "." IN {
type hint;
file "named.ca";
};
zone"rhce.local" IN {
type slave;
file "slaves/rhce.fwd";
masters { 192.168.1.100; };
};
zone"1.168.192.in-addr.arpa" IN {
type slave;
file "slaves/rhce.rev";
masters { 192.168.1.100; };
};
include "/etc/named.rfc1912.zones";
include "/etc/named.root.key";
2. Start the DNS Service
[root@secondary ~]# service named start
Generating /etc/rndc.key: [ OK ]
Starting named: [ OK ]
[root@secondary ~]# 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@secondary ~]# ls /var/named/slaves/
rhce.fwd rhce.rev
[root@secondary ~]# cat /var/named/slaves/rhce.fwd
$ORIGIN .
$TTL 86400; 1 day
rhce.localIN SOAmasterdns.rhce.local. root.rhce.local. (
2011071001 ; serial
3600 ; refresh (1 hour)
1800 ; retry (30 minutes)
604800 ; expire (1 week)
86400 ; minimum (1 day)
)
NS master.rhce.local.
NS secondary.rhce.local.
A192.168.1.100
A192.168.1.101
A192.168.1.102
$ORIGIN rhce.local.
clientA192.168.1.102
masterA192.168.1.100
secondaryA192.168.1.101
[root@secondary ~]# cat /var/named/slaves/rhce.rev
$ORIGIN .
$TTL 86400; 1 day
1.168.192.in-addr.arpaIN SOAmaster.rhce.local. root.rhce.local. (
2011071001 ; serial
3600 ; refresh (1 hour)
1800 ; retry (30 minutes)
604800 ; expire (1 week)
86400 ; minimum (1 day)
)
NS master.rhce.local.
NS secondary.rhce.local.
PTRrhce.local.
$ORIGIN 1.168.192.in-addr.arpa.
100PTRmaster.rhce.local.
101PTRsecondary.rhce.local.
102PTRclient.rhce.local.
clientA192.168.1.102
masterA192.168.1.100
secondaryA192.168.1.101
3. Add the DNS Server details to all systems
[root@secondary ~]# vi /etc/resolv.conf
# Generated by NetworkManager
search rhce.com
nameserver 192.168.1.100
nameserver 192.168.1.101
nameserver 8.8.8.8
4. Test DNS Server
[root@secondary ~]# dig masterdns.rhce.local
; <<>> DiG 9.8.2rc1-RedHat-9.8.2-0.10.rc1.el6_3.6 <<>> master.rhce.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:
;master.rhce.local.INA
;; ANSWER SECTION:
master.rhce.local. 86400INA192.168.1.100
;; AUTHORITY SECTION:
rhce.local.86400INNSmaster.rhce.local.
rhce.local.86400INNSsecondary.rhce.local.
;; ADDITIONAL SECTION:
secondary.rhce.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@secondary ~]# dig secondary.rhce.local
; <<>> DiG 9.8.2rc1-RedHat-9.8.2-0.10.rc1.el6_3.6 <<>> secondary.rhce.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:
;secondary.rhce.local.INA
;; ANSWER SECTION:
secondary.rhce.local. 86400 INA192.168.1.101
;; AUTHORITY SECTION:
rhce.local.86400INNSmaster.rhce.local.
rhce.local.86400INNSsecondary.rhce.local.
;; ADDITIONAL SECTION:
master.rhce.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@secondary ~]# nslookup rhce.local
Server:192.168.1.100
Address:192.168.1.100#53
Name:rhce.local
Address: 192.168.1.101
Name:rhce.local
Address: 192.168.1.102
Name:rhce.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 rhce]# vi /etc/resolv.conf
# Generated by NetworkManager
search rhce.local
nameserver 192.168.1.100
nameserver 192.168.1.101
nameserver 8.8.8.8
Test DNS Server
[root@client rhce]# dig master.rhce.local
; <<>> DiG 9.8.2rc1-RedHat-9.8.2-0.10.rc1.el6 <<>> master.rhce.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:
;master.rhce.local.INA
;; ANSWER SECTION:
master.rhce.local. 86400INA192.168.1.100
;; AUTHORITY SECTION:
rhce.local.86400INNSmaster.rhce.local.
rhce.local.86400INNSsecondary.rhce.local.
;; ADDITIONAL SECTION:
secondary.rhce.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 rhce]# dig secondary.rhce.local
; <<>> DiG 9.8.2rc1-RedHat-9.8.2-0.10.rc1.el6 <<>> secondary.rhce.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:
;secondary.rhce.local.INA
;; ANSWER SECTION:
secondary.rhce.local. 86400 INA192.168.1.101
;; AUTHORITY SECTION:
rhce.local.86400INNSsecondary.rhce.local.
rhce.local.86400INNSmaster.rhce.local.
;; ADDITIONAL SECTION:
master.rhce.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 rhce]# dig client.rhce.local
; <<>> DiG 9.8.2rc1-RedHat-9.8.2-0.10.rc1.el6 <<>> client.rhce.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.rhce.local.INA
;; ANSWER SECTION:
client.rhce.local.86400INA192.168.1.102
;; AUTHORITY SECTION:
rhce.local.86400INNSmaster.rhce.local.
rhce.local.86400INNSsecondary.rhce.local.
;; ADDITIONAL SECTION:
master.rhce.local. 86400INA192.168.1.100
secondary.rhce.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 rhce]# nslookup rhce.local
Server:192.168.1.100
Address:192.168.1.100#53
Name:rhce.local
Address: 192.168.1.102
Name:rhce.local
Address: 192.168.1.100
Name:rhce.local
Address: 192.168.1.101
Now the primary and secondary DNS servers are ready to use.
