Step by step DNS Configuration on Linux RHEL.

In this document, we are going to discuss about How to configure Domain Name Server(DNS) configre. Later the same DNS configuration going to use Oracle 11g Release 2 Real Application Cluster (RAC) Installations.

--------------------------------------------------------------------------------

Step 1 : Login as root and install below listed Bind RPM's.

rpm -Uvh bind-9.3.3-7.el5.i386.rpm \

bind-chroot-9.3.3-7.el5.i386.rpm \

bind-devel-9.3.3-7.el5.i386.rpm \

bind-libbind-devel-9.3.3-7.el5.i386.rpm \

bind-libs-9.3.3-7.el5.i386.rpm \

bind-sdb-9.3.3-7.el5.i386.rpm \

system-config-bind-4.0.3-2.el5.noarch.rpm \

caching-nameserver-9.3.3-7.el5.i386.rpm \

postgresql-libs-8.1.4-1.1.i386.rpm

 

Step 2: Verify the IP address for the DNS server. Use following command to check the IP address.

[root@dns ~]# ifconfig

eth0 Link encap:Ethernet HWaddr 00:0C:29:7D:60:F3

inet addr:192.168.1.100 Bcast:192.168.1.255 Mask:255.255.255.0

inet6 addr: fe80::20c:29ff:fe7d:60f3/64 Scope:Link

UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1

RX packets:28 errors:0 dropped:0 overruns:0 frame:0

TX packets:39 errors:0 dropped:0 overruns:0 carrier:0

collisions:0 txqueuelen:1000

RX bytes:4919 (4.8 KiB) TX bytes:5628 (5.4 KiB)

Interrupt:67 Base address:0x2024

Step 3: There are four files we have to edit. Find the below easy steps to configure the DNS server.

1. Create a named.conf file using sample named.caching-nameserver.conf file.

[root@dns ~]# cd /var/named/chroot/etc/

[root@dns etc]# ls

localtime named.caching-nameserver.conf named.rfc1912.zones rndc.key

[root@dns etc]#cp named.caching-nameserver.conf named.conf

2. Edit the named.conf file based on your configuration. For example.

options {

listen-on port 53 { 192.168.1.100; };

# 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";

        // Those options should be used carefully because they disable port

        // randomization

        // query-source port 53;

        // query-source-v6 port 53;

        allow-query { any; };

        allow-query-cache { localhost; };

        };

logging {

        channel default_debug {

        file "data/named.run";

        severity dynamic;

        };

};

view localhost_resolver {

        match-clients { any; };

        match-destinations { 192.168.1.100; };

        recursion yes;

        include "/etc/named.rfc1912.zones";

};

3. Edit named.rfc1912.zones file. Sample file given below.

zone "." IN {

              type hint;

              file "named.ca";

};

zone "india.com" IN {

                 type master;

                 file "forward.zone";

                 allow-update { none; };

};

zone "localhost" IN {

                 type master;

                 file "localhost.zone";

                 allow-update { none; };

};

zone "1.168.192.in-addr.arpa" IN {

                 type master;

                 file "reverse.zone";

                 allow-update { none; };

};

..

4. Change the permission to the above two files.

chgrp named named.conf

5. Change the directory to below location

cd /var/named/chroot/var/named

cp localdomain.zone forward.zone

cp named.local reverse.zone

 

6. Modify the forward.zone file. example

$TTL 86400

@          IN     SOA    dns.india.com.  root.dns.india.com. (

                         42 ; serial (d. adams)

                         3H ; refresh

                        15M ; retry

                         1W ; expiry

                         1D ) ; minimum

          IN   NS     dns.india.com.

dns       IN   A      192.168.1.100

 

7. Modify the reverse.zone file

$TTL 86400

@        IN     SOA    dns.india.com.    root.dns.india.com. (

                       1997022700 ; Serial

                            28800 ; Refresh

                            14400 ; Retry

                          3600000 ; Expire

                          86400 ) ; Minimum

         IN   NS   dns.india.com.

100      IN   PTR  dns.india.com.

8. Change the ownership for both the files.

chgrp named reverse.zone

chgrp named forward.zone

9. make an entry to both /etc/hosts and /etc/resolve.conf files. The samples are below.

cat /etc/hosts

192.168.1.100 dnc.india.com dnc

cat /etc/resolve.conf

search india.com

namedserver 192.168.1.100

10. Restart the named services using below statement.

service named restart

11. Verify the DNS server using below statements

[root@dns named]# dig dnc.india.com

; «» DiG 9.3.6-P1-RedHat-9.3.6-4.P1.el5_4.2 «» dns.india.com

;; global options: printcmd

;; Got answer:

;; -»HEADER«- opcode: QUERY, status: NOERROR, id: 1483

;; flags: qr aa rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 1, ADDITIONAL: 0

;; QUESTION SECTION:

;dns.india.com. IN A

;; ANSWER SECTION:

dns.india.com. 86400 IN A 192.168.1.100

;; AUTHORITY SECTION:

india.com. 86400 IN NS dns.india.com.

;; Query time: 1 msec

;; SERVER: 192.168.1.100#53(192.168.1.100)

;; WHEN: Mon Aug 27 23:54:49 2012

;; MSG SIZE rcvd: 61

12. To check reverse the zone

[root@dns named]# dig -x 192.168.1.100

; «» DiG 9.3.6-P1-RedHat-9.3.6-4.P1.el5_4.2 «» -x 192.168.1.100

;; global options: printcmd

;; Got answer:

;; -»HEADER«- opcode: QUERY, status: NOERROR, id: 55949

;; flags: qr aa rd ra; QUERY: 1, ANSWER: 2, AUTHORITY: 1, ADDITIONAL: 1

;; QUESTION SECTION:

;100.1.168.192.in-addr.arpa. IN PTR

;; ANSWER SECTION:

100.1.168.192.in-addr.arpa. 86400 IN PTR dnc-priv.india.com.

100.1.168.192.in-addr.arpa. 86400 IN PTR dnc.india.com.

;; AUTHORITY SECTION:

1.168.192.in-addr.arpa. 86400 IN NS dnc.india.com.

;; ADDITIONAL SECTION:

dns.india.com. 86400 IN A 192.168.1.100

;; Query time: 1 msec

;; SERVER: 192.168.1.100#53(192.168.1.100)

;; WHEN: Mon Aug 27 23:57:27 2012

;; MSG SIZE rcvd: 124

13. To verify DNS Server using nslookup

[root@dns named]# nslookup dnc.india.com

Server: 192.168.1.100

Address: 192.168.1.100#53

Name: dns.india.com

Address: 192.168.1.100

DNS server working fine now. Finally we got success.

14. For Oracle 11gR2 RAC Installation adding node Information in /var/named/chroot/var/named/forward.zone file on DNS server.

$TTL    86400

@               IN SOA  dns.india.com. root.dns.india.com. (

                                        42              ; serial (d. adams)

                                        3H              ; refresh

                                        15M             ; retry

                                        1W              ; expiry

                                        1D )            ; minimum

                IN NS           dns.india.com.

dnc             IN A            192.168.1.100

kracnode1       IN A    192.168.1.50

kracnode2       IN A    192.168.1.51

kracnode1-vip   IN A    192.168.1.60

kracnode2-vip   IN A    192.168.1.61

kracnode-scan   IN A    192.168.1.70

kracnode-scan   IN A    192.168.1.71

kracnode-scan   IN A    192.168.1.72

15.  Restart named service as a root user.

[root@dns named]# service named restart

Stopping named:                                            [  OK  ]

Starting named:                                            [  OK  ]

16. Verify the SCAN names using nslookup.

[root@dns named]# nslookup kracnode-scan

Server:         192.168.1.100

Address:        192.168.1.100#53

Name:   kracnode-scan.india.com

Address: 192.168.1.72

Name:   kracnode-scan.india.com

Address: 192.168.1.70

Name:   kracnode-scan.india.com

Address: 192.168.1.71

17. Add below files in /etc/resolv.conf  file on all the nodes.

search india.com

nameserver 192.168.1.100

[oracle@krac1 ]# cat /etc/resolv.conf

search india.com

nameserver 192.168.1.100

[root@krac1 bin]# nslookup kracnode-scan

Server:         192.168.1.100

Address:        192.168.1.100#53

Name:   kracnode-scan.india.com

Address: 192.168.1.71

Name:   kracnode-scan.india.com

Address: 192.168.1.72

Name:   kracnode-scan.india.com

Address: 192.168.1.70

18. DNS server ready for Oracle 11gR2 RAC setup.