Configure SCAN DNS for RAC 11G RAC 12C using dnsmasq in OEL5, OEL6, OEL7

Posted on November 1, 2013 by joda3008

Configuration of network for virtualbox and RAC is always making a lot of trouble and raises many questions. In this article I’ll show how to setup network for RAC 11G, 12C using dnsmasq.

Objectives to complete:

full network setup for RAC
- public network
- private network
- SCAN settings resolved by dnsmasq
full access to internet from each RAC hosts
- internet network
configure dnsmasq

In my articles for RAC I usually have three network cards for each of my node with following settings on VirtualBox

Adapter1 – used for public RAC interface

Adapter2 – used for private RAC interface

Adapter3 – used for internet connections

and two host machines with following settings

rac1.dbaora.com
rac2.dbaora.com

	public	private	vip
rac1	192.168.0.50	192.168.56.60	192.168.0.70
rac2	192.168.0.51	192.168.56.61	192.168.0.71

with single client access name (SCAN) address

	public
rac-scan	192.168.0.20 192.168.0.21 192.168.0.22

My WIFI router generates ip adress like 192.168.1.X so it doesn’t interfere with RAC public, private and SCAN. It’s important to have your internet network on separate subnet.

So my entry in “/ect/hosts” looks following. As you can notice SCAN entries are commented and will be resolved via dnsmasq.

127.0.0.1     localhost.localdomain localhost

#public
192.168.0.50   rac1        rac1.dbaora.com
192.168.0.51   rac2        rac2.dbaora.com

#private
192.168.56.60  rac1-priv   rac1-priv.dbaora.com 
192.168.56.61  rac2-priv   rac2-priv.dbaora.com

#virtual
192.168.0.70   rac1-vip    rac1-vip.dbaora.com
192.168.0.71   rac2-vip    rac2-vip.dbaora.com

#scan
#192.168.0.20   rac-scan    rac-scan.dbaora.com
#192.168.0.21   rac-scan    rac-scan.dbaora.com
#192.168.0.22   rac-scan    rac-scan.dbaora.com

Install and configure dnsmasq

1. To install dnsmasq run as root following command

yum install dnsmasq

2. Configure dnsmasq

create new file “/etc/racdns” with settings for SCAN

[root@rac1 ~]# cat /etc/racdns
#scan
192.168.0.20   rac-scan    rac-scan.dbaora.com
192.168.0.21   rac-scan    rac-scan.dbaora.com
192.168.0.22   rac-scan    rac-scan.dbaora.com

modify dnsmasq default configuration file “/etc/dnsmasq.conf”. One parameter addn-hosts should be changed to point to file “/etc/racdns”.

[root@rac1 ~]# cat /etc/dnsmasq.conf | grep addn-hosts
addn-hosts=/etc/racdns

3. Start dnsmasq

service dnsmasq start
chkconfig dnsmasq on

4. Next step is to resolve problem with file “/etc/resolv.conf”

I’m using third network card as NAT with DHCP so each time you restart network card or reboot host the file is overwritten with automatically generated settings. Nameserver points for 192.168.1.1 which is required to resolve internet entries but not enough to resolve SCAN settings via dnsmasq.

[root@rac1 ~]# cat /etc/resolv.conf
# Generated by Networkmanager
search dbaora.com
nameserver 192.168.1.1

As default dnsmasq is running on ip adress 127.0.0.1 so it requires following settings in “/etc/resolv.conf”.

[root@rac1 ~]# cat /etc/resolv.conf
# Generated by Networkmanager
nameserver 127.0.0.1
search dbaora.com
nameserver 192.168.1.1

You must protect the file from being automatically overwritten by host reboot, network card restart etc.

[root@rac1 ~]# chattr +i /etc/resolv.conf

Verification

It’s just running nslookup to verify all is working fine

rac-scan

[root@rac1 ~]# nslookup rac-scan
Server:        127.0.0.1
Address:    127.0.0.1#53

Name:    rac-scan.dbaora.com
Address: 192.168.0.22
Name:    rac-scan.dbaora.com
Address: 192.168.0.20
Name:    rac-scan.dbaora.com
Address: 192.168.0.21

[root@rac1 ~]# nslookup rac-scan
Server:        127.0.0.1
Address:    127.0.0.1#53

Name:    rac-scan.dbaora.com
Address: 192.168.0.20
Name:    rac-scan.dbaora.com
Address: 192.168.0.21
Name:    rac-scan.dbaora.com
Address: 192.168.0.22

[root@rac1 ~]# nslookup rac-scan
Server:        127.0.0.1
Address:    127.0.0.1#53

Name:    rac-scan.dbaora.com
Address: 192.168.0.21
Name:    rac-scan.dbaora.com
Address: 192.168.0.22
Name:    rac-scan.dbaora.com
Address: 192.168.0.20

rac1, rac2, rac1-priv, rac2-priv, rac1-vip, rac2-vip

[root@rac1 ~]# nslookup rac1
Server:        127.0.0.1
Address:    127.0.0.1#53

Name:    rac1.dbaora.com
Address: 192.168.0.50

[root@rac1 ~]# nslookup rac2
Server:        127.0.0.1
Address:    127.0.0.1#53

Name:    rac2.dbaora.com
Address: 192.168.0.51

[root@rac1 ~]# nslookup rac1-priv
Server:        127.0.0.1
Address:    127.0.0.1#53

Name:    rac1-priv.dbaora.com
Address: 192.168.56.60

[root@rac1 ~]# nslookup rac2-priv
Server:        127.0.0.1
Address:    127.0.0.1#53

Name:    rac2-priv.dbaora.com
Address: 192.168.56.61

[root@rac1 ~]# nslookup rac1-vip
Server:        127.0.0.1
Address:    127.0.0.1#53

Name:    rac1-vip.dbaora.com
Address: 192.168.0.70

[root@rac1 ~]# nslookup rac2-vip
Server:        127.0.0.1
Address:    127.0.0.1#53

Name:    rac2-vip.dbaora.com
Address: 192.168.0.71

Have a fun 🙂

Tomasz

44 thoughts on “Configure SCAN DNS for RAC 11G RAC 12C using dnsmasq in OEL5, OEL6, OEL7”

Adnan Rafi on December 11, 2013 at 4:02 am said:

Superb method, do we need to configure dnsmasq on all Rac Nodes?

Reply ↓
- admin on December 11, 2013 at 8:17 am said:
  
  yes on each rac node 🙂
  
  Reply ↓
- Rahul on August 2, 2014 at 8:59 am said:
  
  Thanks you are my saviour
  
  Reply ↓
  - admin on August 2, 2014 at 9:42 am said:
    
    🙂
    
    Reply ↓
Rafael on March 11, 2014 at 2:35 am said:

Hi,
I’m trying to create an ora rac lab using three Vmware fusion machines:
– dnsmasq (OEL 6.5) dnsserver
– oragrid + ora rdbms (RHEL 5.5) node 1
– oragrid + ora rdbms (RHEL 5.5) node 1
– mac os (Virtual disk – NFS)

I’ve the following error when I try to install Ora Grid Infrastructure:
INS-40922 Invalid Scan Name – Unresolvable to IP address

127.0.0.1 localhost.localdomain localhost
#### public
192.168.0.31 racnode1 racnode1.rafadomain
192.168.0.32 racnode2 racnode2.rafadomain
#### private
192.168.56.1 racnode1-priv racnode1-priv.rafadomain
192.168.56.2 racnode2-priv racnode2-priv.rafadomain
#### virtual
192.168.0.41 racnode1-vip racnode1-vip.rafadomain
192.168.0.42 racnode2-vip racnode2-vip.rafadomain
#### scan
#192.168.0.20 rac-scan rac-scan.rafadomain
#192.168.0.21 rac-scan rac-scan.rafadomain
#192.168.0.22 rac-scan rac-scan.rafadomain

Tks
Rafael

Reply ↓
- admin on March 11, 2014 at 8:22 am said:
  
  Have you verified ip address on each node using nslookup ? Remember dnsmasq must be installed on each node. On each node each ipadrees must be resolveable.
  
  Regards
  Tomasz
  
  Reply ↓
prasant on March 19, 2014 at 10:06 am said:

you are a gem, for last many days i am unsuccessful… but with this i get it done in 10mins

u make my day…. Many many thanks

i didn’t mention the named server in /etc/resolv.conf as i don’t connect to outer world from the vm. is it going to be any problem?

Reply ↓
- admin on March 19, 2014 at 10:52 am said:
  
  If test pings work then all should work
  
  Reply ↓
Hassan Parthasarathy on May 13, 2014 at 4:19 am said:

Nice Article. Thanks. Really helped!
Partha

Reply ↓
- admin on May 13, 2014 at 7:52 am said:
  
  Cool 🙂
  
  Reply ↓
Pingback: Configuring a private DNS server on Openfiler for use with Oracle RAC 12C on Virtual Boxes | Jobacle
james on August 5, 2014 at 9:59 pm said:

This was a great workaround to get a lab rac running with SCAN , thanks

Reply ↓
chandu on August 19, 2014 at 10:44 am said:

I have created a similar setup. And I read somewhere that we shouldnt be able to ping from node1 to node2 or viceversa using the virtual IP’s before installing the grid software.

1) I got the following error while I was about to install Oracle grid software on node 1.
INS-40912] Virtual host name: rac2-vip.localdomain is assigned to another system on the network.

this is my network setup
27.0.0.1 localhost.localdomain localhost
# Public
192.168.0.111 ol6-112-rac1.localdomain ol6-112-rac1
192.168.0.112 ol6-112-rac2.localdomain ol6-112-rac2
# Private
192.168.1.111 ol6-112-rac1-priv.localdomain ol6-112-rac1-priv
192.168.1.112 ol6-112-rac2-priv.localdomain ol6-112-rac2-priv
# Virtual
192.168.0.113 ol6-112-rac1-vip.localdomain ol6-112-rac1-vip
192.168.0.114 ol6-112-rac2-vip.localdomain ol6-112-rac2-vip
# SCAN
192.168.0.115 ol6-112-scan.localdomain ol6-112-scan
192.168.0.116 ol6-112-scan.localdomain ol6-112-scan
192.168.0.117 ol6-112-scan.localdomain ol6-112-scan

i am not able to ping to 192.168.0.113, but able to ping to 192.168.0.114 from both the nodes. I have tried emulating your dnsmasq setup but the error still persists. could you help ?

Reply ↓
- chandu on August 19, 2014 at 10:46 am said:
  
  correct , it is
  127.0.0.1 localhost.localdomain **
  
  Reply ↓
sikandar on August 27, 2014 at 7:51 am said:

hi
how can I use these network settings in vmware workstation 9 ?
I mean ( internal network = ? in workstaion9)
thx in advance

Reply ↓
- admin on August 27, 2014 at 3:10 pm said:
  
  I’m not using workstation but I believe settings should be quite similar to virtual box.
  
  Regards
  Tomasz
  
  Reply ↓
Nagappan on October 17, 2014 at 9:10 am said:

Excellent Article….

Reply ↓
azahari on November 22, 2014 at 12:24 am said:

great notes. I followed as described as solved my issue.

Reply ↓
aran on May 7, 2015 at 12:46 pm said:

Thanks for your notes. I got stressed to setup dns in my Vbox, but I see your notes, its easy to understand and follow..

Reply ↓
Shakeel on September 15, 2015 at 2:04 pm said:

I am installing Oracle 11.2.0.3 Single Node RAC on RHEL 5.3.
I configured DNS as you suggested, but getting following error when run runcluvfy.
“PRVF-5636 : The DNS response time for an unreachable node exceeded “15000” ms on following nodes: RAC-A

Reply ↓
- admin on September 15, 2015 at 2:34 pm said:
  
  My guess is you have slow network or computer that causes such issues.
  
  Reply ↓
Shakeel on September 16, 2015 at 1:14 pm said:

I checked on another forum, they suggested to install bind-* packages and start named service. I installed these packages but when start named service, giving this error.
rndc: connect failed: 127.0.0.1#953: connection refused
named is stopped

named.conf not present in /etc and /var/named/chroot/etc locations. Very strange.
How can I solve this problem to clean install? Otherwise, it will install cluster but with failure of some components/warnings.

Reply ↓
Michael on September 18, 2015 at 9:26 pm said:

Thanks a lot your a STAR!

Reply ↓
Anthony on September 27, 2015 at 6:11 pm said:

Superb!! Thanks a lot..

Reply ↓
shyam kumar on October 31, 2015 at 1:17 pm said:

Thank you very much 🙂

Reply ↓
Jay on March 25, 2016 at 9:26 pm said:

Great…. the simplest and easiest method.

Many thanks…

Reply ↓
jeevan on April 15, 2016 at 7:26 pm said:

After lot of effort i got this ..Thanks for post man…

Reply ↓
jeevan on April 16, 2016 at 1:43 am said:

After setting 127.0.0.1 to namedserver my internet is not working,can you please help on this.

Thanks

Reply ↓
jeevan on April 16, 2016 at 3:56 am said:

Thanks,got it fixed…

Reply ↓
Narayanan on April 23, 2016 at 3:07 pm said:

Nice article…..I have been working on the scan issues for 2 days with out any success….your article and explanation save me time and resolved the issue……..Good work….

Reply ↓
Chakravarthi on July 3, 2016 at 6:58 am said:

You are excellent and you are making many life easy.. please post as many as.. I really think people as GOD when they teach things easy and share it with others.

Reply ↓
B on August 20, 2016 at 2:57 pm said:

Thank you for the simplicity in configuring the DNS for rac installation. Like the other comments left you made my day. My greetings.

Reply ↓
Riz on October 23, 2016 at 10:47 am said:

Hi,
After configuring the DNS with dnsmasq ,should the SCAN entries remain commented in the /etc/hosts file?
Thanks!

Reply ↓
- joda3008 on October 26, 2016 at 10:05 am said:
  
  You can keep them
  
  Regards
  Tomasz
  
  Reply ↓
Anzo on April 21, 2017 at 6:23 pm said:

GREAT WORK!
THIS MESSAGE IS PRINTED FOR A REASON, TO SHOW MY APPRECIATION FOR YOUR WORK.
I HAVE BEEN TRY TO INSTALL RAC FOR ALMOST ONE YEAR NOW.

Reply ↓
GAVIN SOORMA on June 26, 2017 at 2:45 am said:

Good work man!

Reply ↓
loilm on February 18, 2019 at 3:48 pm said:

Thanks for u

Reply ↓
Abdul Wahab on March 7, 2019 at 1:56 pm said:

Hello,
One of the most valuable piece of information in installing Oracle RAC!!
It made RAC network configuration very simple.
Thanks a lot for this awesome contribution.

Regards,
Abdul

Reply ↓
Lex on March 13, 2019 at 8:42 am said:

Idk how all you guys are able to connect. I am still having trouble with the networking. I have been at this for a week now. I followed your steps and tried to imitate you and put three NIC cards with the first two internal and the last NAT and I cannot connect to the internet now. Not sure what’s going on. Do you have any advice or youtube videos?

Reply ↓
Lex on March 13, 2019 at 8:44 am said:

testing..not sure if my last post worked..

Reply ↓
Meckhel on April 16, 2020 at 3:28 pm said:

hello, very good writeup and i have followed the steps but when i check the dnsmasq service it shows failed.

[root@pluto-rac1 ~]# chkconfig dnsmasq on
Note: Forwarding request to ‘systemctl enable dnsmasq.service’.
Created symlink from /etc/systemd/system/multi-user.target.wants/dnsmasq.service to /usr/lib/systemd/system/dnsmasq.service.
[root@pluto-rac1 ~]# service dnsmasq status
Redirecting to /bin/systemctl status dnsmasq.service
● dnsmasq.service – DNS caching server.
Loaded: loaded (/usr/lib/systemd/system/dnsmasq.service; enabled; vendor preset: disabled)
Active: failed (Result: exit-code) since Thu 2020-04-16 23:24:20 +08; 1min 27s ago
Main PID: 3157 (code=exited, status=2)

Apr 16 23:24:20 pluto-rac1.blueorigin.com systemd[1]: Started DNS caching server..
Apr 16 23:24:20 pluto-rac1.blueorigin.com dnsmasq[3157]: dnsmasq: failed to create listening socket for port 53: Address already in use
Apr 16 23:24:20 pluto-rac1.blueorigin.com systemd[1]: dnsmasq.service: main process exited, code=exited, status=2/INVALIDARGUMENT
Apr 16 23:24:20 pluto-rac1.blueorigin.com systemd[1]: Unit dnsmasq.service entered failed state.
Apr 16 23:24:20 pluto-rac1.blueorigin.com systemd[1]: dnsmasq.service failed.

Reply ↓
- Meckhel on April 17, 2020 at 3:33 am said:
  
  Can you guide how to create a statis ip address in dnsmasq instead of 127.0.0.1?
  
  dnsmasq: failed to create listening socket for 192.168.0.1: Cannot assign requested address
  
  Reply ↓
Albert on June 29, 2020 at 4:08 pm said:

Great article! Thanks a lot!

Reply ↓
sandeep on July 8, 2024 at 12:29 pm said:

PRVG-11826 : DNS resolved IP addresses “” for SCAN name “sqascan” not found in the name service returned IP addresses “10.226.147.202” – Cause: The name resolution setup check for the indicated SCAN name failed because one or more of the indicated IP addresses obtained from DNS could not be found in the IP addresses obtained from the name service on the system as configured in the ”/etc/nsswitch.conf” configuration file.

Got this issue while installing 12C grid . I have sqascan ip entries in /etc/hosts and /etc/resolve.conf but this is not resolving

Reply ↓

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Configure SCAN DNS for RAC 11G RAC 12C using dnsmasq in OEL5, OEL6, OEL7

44 thoughts on “Configure SCAN DNS for RAC 11G RAC 12C using dnsmasq in OEL5, OEL6, OEL7”

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