Introduction
BIND Installation
BIND Configuratoin
Configure DNS on Hosts
Introduction
What is a DNS Server ?
DNS = Domain Naming Service (or) Domain Name System DNS will resolve the host name for the particular IP address across an organization.
This article provides the basic DNS configuration steps necessary to use the Single Client Access Name (SCAN) introduced in Oracle 11g Release 2 RAC.
Here we will be using a separate linux Server to setup the DNS using BIND
Create a VM and install Linux 6 on it. Click here for installation steps.
Below is the Linux version which we will be using in this setup:
BIND Installation
Assuming there is internet connectivity for your machine, install the DNS server (BIND):
Make the following changes in /etc/named.conf file:
Listen-on: Add the IP of local server on which DNS port which will be answered.
NOTE: If you are using more IP subnets you will have to add reverse DNS for each and every subnet.
Here is the full file content of my config file:
Setup DNS Zone -1 (Forward Lookup):
List the files and see the permissions and group of those created zone files:
Log in to one of the host machines, here we are doing the DNS settings on rac1.oracleapps.com
Right-Click network Icon on task bar and select Edit Connections
Select System eth0 -> Edit
Check Connect automatically
Click tab IPv4 Settings
Select Method to Manual from drop down list, then click Add and fill the following fields:
Address: 192.168.0.101, Netmask: 255.255.255.0, Gateway: 192.168.0.1, DNS Servers: 192.168.0.67, Search domains: oracleapps.com
Click Apply
Select System eth1 -> Edit then Check Connect automatically
Click tab IPv4 Settings
Select Method to Manual from drop down list, then click Add and fill the following fields:
Address: 192.168.1.101, Netmask: 255.255.255.0, Gateway: 192.168.1.1, DNS Servers: 192.168.0.67, Search domains: oracleapps.com
Click Apply
Now restart the network cards, file /etc/resolv.conf should reflect the nameserver and search entries:
BIND Installation
BIND Configuratoin
Configure DNS on Hosts
Introduction
What is a DNS Server ?
DNS = Domain Naming Service (or) Domain Name System DNS will resolve the host name for the particular IP address across an organization.
This article provides the basic DNS configuration steps necessary to use the Single Client Access Name (SCAN) introduced in Oracle 11g Release 2 RAC.
Here we will be using a separate linux Server to setup the DNS using BIND
Create a VM and install Linux 6 on it. Click here for installation steps.
Below is the Linux version which we will be using in this setup:
[root@dns ~]# lsb_release -a
LSB Version: :base-4.0-amd64:base-4.0-noarch:core-4.0-amd64:core-4.0-noarch:graphics-4.0-amd64:graphics-4.0-noarch:printing-4.0-amd64:printing-4.0-noarch
Distributor ID: OracleServer
Description: Oracle Linux Server release 6.7
Release: 6.7
Codename: n/a
And we will use the below Hostname & IP address for the DNS Server:
IP Address : 192.168.0.67 Hostname : dns.oracleapps.comFollowing are the node machines which we will be configuring in the DNS Server for resolving:
IP Address : 192.168.0.101 ## Hostname : rac1.oracleapps.com IP Address : 192.168.0.102 ## Hostname : rac2.oracleapps.com IP Address : 192.168.0.111 ## Hostname : rac1-vip.oracleapps.com IP Address : 192.168.0.112 ## Hostname : rac2-vip.oracleapps.com IP Address : 192.168.1.101 ## Hostname : rac1-priv.oracleapps.com IP Address : 192.168.1.102 ## Hostname : rac1-priv.oracleapps.com IP Address : 192.168.0.121 ## Hostname : rac-scan.oracleapps.com IP Address : 192.168.0.122 ## Hostname : rac-scan.oracleapps.com IP Address : 192.168.0.123 ## Hostname : rac-scan.oracleapps.com IP Address : 192.168.0.201 ## Hostname : apps1.oracleapps.com IP Address : 192.168.0.202 ## Hostname : apps2.oracleapps.comSteps that need to be performed on DNS Server:
BIND Installation
Assuming there is internet connectivity for your machine, install the DNS server (BIND):
[root@dns ~]# yum install bind* -yBIND Configuration
Make the following changes in /etc/named.conf file:
Listen-on: Add the IP of local server on which DNS port which will be answered.
listen-on port 53 { 127.0.0.1; 192.168.0.67;};
Allow-query: change it from { localhost; } to { any; }allow-query { any; };
Configure DNS zones(Forward Lookup): Now we will have to create zone files in which DNS records will be configured. Add following lines in named.conf file:
zone "oracleapps.com" IN {
type master;
file "oracleapps.com.zone";
allow-update { none; };
};
Configure DNS zones(Reverse Lookup): After adding Forward lookup we will now have to configure reverse DNS. Add following in named.conf file:
zone"0.168.192.in-addr.arpa" IN {
type master;
file "0.168.192.in-addr.arpa.zone";
allow-update { none; };
};
zone"1.168.192.in-addr.arpa" IN {
type master;
file "1.168.192.in-addr.arpa.zone";
allow-update { none; };
};
Here, in my setup I am using two different IP subnet’s for databases, they are 192.168.0.x and 192.168.1.x. So I have added records for both.NOTE: If you are using more IP subnets you will have to add reverse DNS for each and every subnet.
Here is the full file content of my config file:
[root@dns ~]# 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; 192.168.0.67;};
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 { any; };
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 "oracleapps.com" IN {
type master;
file "oracleapps.com.zone";
allow-update { none; };
};
zone"0.168.192.in-addr.arpa" IN {
type master;
file "0.168.192.in-addr.arpa.zone";
allow-update { none; };
};
zone"1.168.192.in-addr.arpa" IN {
type master;
file "1.168.192.in-addr.arpa.zone";
allow-update { none; };
};
include "/etc/named.rfc1912.zones";
include "/etc/named.root.key";
Now we will create the zone files which we mentioned in named.conf:Setup DNS Zone -1 (Forward Lookup):
[root@dns ~]# cd /var/named [root@dns named]# cat oracleapps.com.zone $TTL 86400 @ IN SOA dns.oracleapps.com. root.oracleapps.com. ( 2014051001 ; serial 3600 ; refresh 1800 ; retry 604800 ; expire 86400 ; minimum ) @ IN NS dns.oracleapps.com. dns IN A 192.168.0.67 rac1 IN A 192.168.0.101 rac2 IN A 192.168.0.102 rac1-vip IN A 192.168.0.111 rac2-vip IN A 192.168.0.112 rac1-priv IN A 192.168.1.101 rac2-priv IN A 192.168.1.102 rac-scan IN A 192.168.0.121 rac-scan IN A 192.168.0.122 rac-scan IN A 192.168.0.123 apps1 IN A 192.168.0.201 apps2 IN A 192.168.0.202Setup DNS Zone -2 (Reverse Lookup for subnet 192.168.0.x):
[root@dns named]# cat 0.168.192.in-addr.arpa.zone $TTL 86400 @ IN SOA dns.oracleapps.com. root.oracleapps.com. ( 2014051001 ; serial 3600 ; refresh 1800 ; retry 604800 ; expire 86400 ; minimum ) @ IN NS dns.oracleapps.com. dns IN A 192.168.0.67 67 IN PTR dns.oracleapps.com. 101 IN PTR rac1.oracleapps.com. 102 IN PTR rac2.oracleapps.com. 111 IN PTR rac1-vip.oracleapps.com. 112 IN PTR rac2-vip.oracleapps.com. 121 IN PTR rac-scan.oracleapps.com. 122 IN PTR rac-scan.oracleapps.com. 123 IN PTR rac-scan.oracleapps.com. 201 IN PTR apps1.oracleapps.com. 202 IN PTR apps2.oracleapps.com.Setup DNS Zone -3 (Reverse Lookup for subnet 192.168.1.x):
[root@dns named]# cat 1.168.192.in-addr.arpa.zone $TTL 86400 @ IN SOA dns.oracleapps.com. root.oracleapps.com. ( 2014051001 ; serial 3600 ; refresh 1800 ; retry 604800 ; expire 86400 ; minimum ) @ IN NS dns.oracleapps.com. dns IN A 192.168.0.67 101 IN PTR rac1-priv.oracleapps.com. 102 IN PTR rac2-priv.oracleapps.com.The zone files which we created will be under root group, we need to change those to group "named".
List the files and see the permissions and group of those created zone files:
[root@dns named]# ls -lrt *.zone -rw-r--r--. 1 root root 788 Nov 6 22:10 oracleapps.com.zone -rw-r--r--. 1 root root 914 Nov 6 22:17 0.168.192.in-addr.arpa.zone -rw-r--r--. 1 root root 571 Nov 6 22:19 1.168.192.in-addr.arpa.zoneChange the group to named using below Command:
[root@dns named]# chgrp named /var/named/oracleapps.com.zone [root@dns named]# chgrp named /var/named/0.168.192.in-addr.arpa.zone [root@dns named]# chgrp named /var/named/1.168.192.in-addr.arpa.zoneList the files again:
[root@dns named]# ls -lrt *.zone -rw-r--r--. 1 root named 788 Nov 6 22:10 oracleapps.com.zone -rw-r--r--. 1 root named 914 Nov 6 22:17 0.168.192.in-addr.arpa.zone -rw-r--r--. 1 root named 571 Nov 6 22:19 1.168.192.in-addr.arpa.zoneThen we need to check the Context of the all files which we edited so far:
[root@dns named]# ls -lZd /etc/named.conf -rw-r-----. root named system_u:object_r:named_conf_t:s0 /etc/named.conf [root@dns named]# ls -lZd /var/named/oracleapps.com.zone -rw-r--r--. root named unconfined_u:object_r:named_zone_t:s0 /var/named/oracleapps.com.zone [root@dns named]# ls -lZd /var/named/0.168.192.in-addr.arpa.zone -rw-r--r--. root named unconfined_u:object_r:named_zone_t:s0 /var/named/0.168.192.in-addr.arpa.zone [root@dns named]# ls -lZd /var/named/1.168.192.in-addr.arpa.zone -rw-r--r--. root named unconfined_u:object_r:named_zone_t:s0 /var/named/1.168.192.in-addr.arpa.zoneThey need to be in the context of named_conf_t, if its different, then we need to restore the context using:
[root@dns named] restorecon /etc/named.confNow we need to check if there are any typo errors in the conf file and zone files:
[root@dns named]# named-checkconf /etc/named.conf /etc/named.conf:11: missing ';' before '}'Above if you can see there is typo error at line 11, I fixed it and ran the command again:
[root@dns named]# vi /etc/named.conf [root@dns named]# named-checkconf /etc/named.conf [root@dns named]# named-checkzone oracleapps.com /var/named/oracleapps.com.zone zone oracleapps.com/IN: loaded serial 2014051001 OK [root@dns named]# named-checkzone oracleapps.com /var/named/0.168.192.in-addr.arpa.zone zone oracleapps.com/IN: loaded serial 2014051001 OK [root@dns named]# named-checkzone oracleapps.com /var/named/1.168.192.in-addr.arpa.zone zone oracleapps.com/IN: loaded serial 2014051001 OKOnce everything looks OK, restart the DNS Service:
[root@dns named]# service named restart Stopping named: [ OK ] Generating /etc/rndc.key: [ OK ] Starting named: [ OK ]Make the named Service in runlevels:
[root@dns named]# chkconfig named on [root@dns named]# chkconfig --list named named 0:off 1:off 2:on 3:on 4:on 5:on 6:offDeploy iptables rules to allow DNS service run on port 53:
[root@dns named]# iptables -A INPUT -i lo -j ACCEPT [root@dns named]# iptables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT [root@dns named]# iptables -A INPUT -p tcp -m state --state NEW -m tcp --dport 22 -j ACCEPT [root@dns named]# iptables -A INPUT -p tcp -m state --state NEW -m tcp --dport 53 -j ACCEPT [root@dns named]# iptables -A INPUT -p udp -m state --state NEW -m udp --dport 53 -j ACCEPT [root@dns named]# iptables -A INPUT -j DROPSave the iptables using:
[root@dns named]# service iptables save iptables: Saving firewall rules to /etc/sysconfig/iptables:[ OK ]It is best approach to restart the iptables after a configuration change:
[root@dns named]# service iptables restart iptables: Setting chains to policy ACCEPT: filter [ OK ] iptables: Flushing firewall rules: [ OK ] iptables: Unloading modules: [ OK ] iptables: Applying firewall rules: [ OK ]Make the iptables service in runlevels:
[root@dns named]# chkconfig iptables on [root@dns named]# chkconfig --list iptables iptables 0:off 1:off 2:on 3:on 4:on 5:on 6:offRestart the network interface cards:
[root@dns ~]# service network restart Shutting down interface eth0: Device state: 3 (disconnected) [ OK ] Shutting down loopback interface: [ OK ] Bringing up loopback interface: [ OK ] Bringing up interface eth0: Active connection state: activated Active connection path: /org/freedesktop/NetworkManager/ActiveConnection/2 [ OK ]Set the search domain and nameserver information in the /etc/resolv.conf for IP resolution:
[root@dns ~]# cat /etc/resolv.conf # Generated by NetworkManager search oracleapps.com nameserver 192.168.0.67Check the DNS server using Dig Command:
[root@dns named]# dig dns.oracleapps.com ; <<>> DiG 9.8.2rc1-RedHat-9.8.2-0.62.rc1.el6_9.4 <<>> dns.oracleapps.com ;; global options: +cmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 3506 ;; flags: qr aa rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 1, ADDITIONAL: 0 ;; QUESTION SECTION: ;dns.oracleapps.com. IN A ;; ANSWER SECTION: dns.oracleapps.com. 86400 IN A 192.168.0.67 ;; AUTHORITY SECTION: oracleapps.com. 86400 IN NS dns.oracleapps.com. ;; Query time: 4 msec ;; SERVER: 192.168.0.67#53(192.168.0.67) ;; WHEN: Mon Nov 6 22:27:45 2017 ;; MSG SIZE rcvd: 66Check for IP resolution for all the hosts mentioned in the zone files:
[root@dns named]# nslookup rac1 Server: 192.168.0.67 Address: 192.168.0.67#53 Name: rac1.oracleapps.com Address: 192.168.0.101 [root@dns named]# nslookup rac2 Server: 192.168.0.67 Address: 192.168.0.67#53 Name: rac2.oracleapps.com Address: 192.168.0.102 [root@dns named]# nslookup rac-scan Server: 192.168.0.67 Address: 192.168.0.67#53 Name: rac-scan.oracleapps.com Address: 192.168.0.122 Name: rac-scan.oracleapps.com Address: 192.168.0.123 Name: rac-scan.oracleapps.com Address: 192.168.0.121 [root@dns named]# nslookup rac-scan Server: 192.168.0.67 Address: 192.168.0.67#53 Name: rac-scan.oracleapps.com Address: 192.168.0.123 Name: rac-scan.oracleapps.com Address: 192.168.0.121 Name: rac-scan.oracleapps.com Address: 192.168.0.122Configure DNS for Hosts
Log in to one of the host machines, here we are doing the DNS settings on rac1.oracleapps.com
Right-Click network Icon on task bar and select Edit Connections
Select System eth0 -> Edit
Check Connect automatically
Click tab IPv4 Settings
Select Method to Manual from drop down list, then click Add and fill the following fields:
Address: 192.168.0.101, Netmask: 255.255.255.0, Gateway: 192.168.0.1, DNS Servers: 192.168.0.67, Search domains: oracleapps.com
Click Apply
Select System eth1 -> Edit then Check Connect automatically
Click tab IPv4 Settings
Select Method to Manual from drop down list, then click Add and fill the following fields:
Address: 192.168.1.101, Netmask: 255.255.255.0, Gateway: 192.168.1.1, DNS Servers: 192.168.0.67, Search domains: oracleapps.com
Click Apply
Now restart the network cards, file /etc/resolv.conf should reflect the nameserver and search entries:
[root@rac1 ~]# service network restart [root@rac1 ~]# cat /etc/resolv.conf # Generated by Networkmanager nameserver 192.168.0.64 search oracleapps.com nameserver 192.168.0.1Once everything is setup, now test the IP lookup with nslookup command:
[root@rac1 ~]# nslookup rac1 Server: 192.168.0.67 Address: 192.168.0.67#53 Name: rac1.oracleapps.com Address: 192.168.0.101 [root@rac1 ~]# nslookup rac2 Server: 192.168.0.67 Address: 192.168.0.67#53 Name: rac2.oracleapps.com Address: 192.168.0.102 [root@rac1 ~]# nslookup rac1-priv Server: 192.168.0.67 Address: 192.168.0.67#53 Name: rac1-priv.oracleapps.com Address: 192.168.1.101 [root@rac1 ~]# nslookup ebsrac-scan Server: 192.168.0.67 Address: 192.168.0.67#53 Name: rac-scan.oracleapps.com Address: 192.168.0.123 Name: rac-scan.oracleapps.com Address: 192.168.0.121 Name: rac-scan.oracleapps.com Address: 192.168.0.122 [root@rac1 ~]# nslookup ebsrac-scan Server: 192.168.0.67 Address: 192.168.0.67#53 Name: rac-scan.oracleapps.com Address: 192.168.0.121 Name: rac-scan.oracleapps.com Address: 192.168.0.122 Name: rac-scan.oracleapps.com Address: 192.168.0.123 [root@rac1 ~]# nslookup 192.168.0.101 Server: 192.168.0.67 Address: 192.168.0.67#53 101.0.168.192.in-addr.arpa name = rac1.oracleapps.com. [root@rac1 ~]# nslookup 192.168.1.101 Server: 192.168.0.67 Address: 192.168.0.67#53 101.1.168.192.in-addr.arpa name = rac1-priv.oracleapps.com.You need to do the above settings on each node if you want to use DNS.
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