Nslookup

Question

hi all
i am using oracle database 11g R2
Oracle Grid 11g R2
Oracle Linux 5.5
i want to know about DNS and Scan name.
i read somewhere that for installation purposes we need to define or configure Scan name in /etc/hosts
and i also read that we do not need to configure Scan Name with IP address in /etc/hosts.
and for Rac we need three DNS if yes then how could we configure three DNS and what will be
purpose of these three DNS?
as i configured SCAN NAME in hosts
but when i look for scan name then it just returned lisntener as true without scan name and IP address.
and i also create nslookup script with my scan name and ip address.
192.167.1.187 racnode-cluster-scan
and this the code i used.
#!/bin/bash
HOSTNAME=${1}
if [[ $HOSTNAME = "
racnode-cluster-scan" ]]; then
    echo "Server:         
24.154.1.34"
    echo "Address:        
24.154.1.34#53"
    echo "Non-authoritative answer:"
    echo "Name:   
racnode-cluster-scan"
    echo "Address: 
192.168.1.187"
else
    /usr/bin/nslookup.original $HOSTNAME
fiand here the nslookup result.
[grid@racnode1 ~]$ cluvfy comp scan -verbose
Verifying scan
Checking Single Client Access Name (SCAN)...
  SCAN VIP name     Node          Running?      ListenerName  Port          Running?   
  racnode-cluster-scan  racnode2      true          LISTENER      1521          true       
Checking name resolution setup for "racnode-cluster-scan"...
ERROR:
PRVF-4664 : Found inconsistent name resolution entries for SCAN name "racnode-cluster-scan"
  SCAN Name     IP Address                Status                    Comment  
  racnode-cluster-scan  192.167.1.187             failed                    NIS Entry
ERROR:
PRVF-4657 : Name resolution setup check for "racnode-cluster-scan" (IP address: 192.167.1.187) failed
ERROR:
PRVF-4664 : Found inconsistent name resolution entries for SCAN name "racnode-cluster-scan"
Verification of SCAN VIP and Listener setup failed
Verification of scan was unsuccessful on all the specified nodes.
[grid@racnode1 ~]$ note: i did not configure DNS for my network DNS is empty.
NISHA
Edited by: nisha on May 29, 2011 11:36 AM

Answer 1

Dear Nisha,
as Aman mentioned, you can ignore the warning.
refer the link for configure dns server, if you would like, before doing anything read related documents. theoritical knowledge is more important as practical knowledge.
http://blog.ronnyegner-consulting.de/2009/10/15/configuring-a-small-dns-server-for-scan/
also refer the link:-http://www.oracle-base.com/articles/11g/OracleDB11gR2RACInstallationOnOEL5UsingVMwareServer2.php
The SCAN address should not really be defined in the hosts file. Instead is should be defined on the DNS to round-robin between 3 addresses on the same subnet as the public IPs. For this installation, we will compromise and use the hosts file.
If you are using DNS, then only the first line should be present in the "/etc/hosts" file.
http://www.oracle-base.com/articles/linux/DnsConfigurationForSCAN.php
read and then practice.
all the best