Configure a SCAN IP using DNS for Oracle Grid Infrastructure (Oracle 11gR2)

The SCAN  IP addresses must be on the same subnet as your public network in the cluster. The name must be 15 characters or less in length,not including the domain, and must be resolvable without the domain suffix (for example: “coltdb01-scan’ must be resolvable as opposed to “coltdb01-scan.example.com”).

Follow the steps to configure the SCAN IPs using DNS

1) To identify your DNS server in RHEL 

   [root@coltdb02 ~]# cat /etc/resolv.conf

2) Connect to the DNS server open the DNS administrator window

   

   Start -> Run -> dnsmgmt.msc

3) Right Click on the Domain name and select 'New Host'. Provide the Name and ip as below.

4) Repeat this step for 3 times.You have to create a single name that resolves to 3 IP

   addresses using a round-robin algorithm.

5) You can check the SCAN configuration in DNS using “nslookup”. If your DNS is set up to provide round-robin access to the IPs resolved by the SCAN entry, then run the “nslookup” command at least twice to see the round-robin algorithm work. The result should be that each time, the “nslookup” would return a set of 3 IPs in a different order.

[root@coltdb01 ~]# nslookup coltdb01-scan

Server:         10.91.119.134

Address:        10.91.119.134#53

Name:   coltdb01-scan.example.com

Address: 10.91.119.167

Name:   coltdb01-scan.example.com

Address: 10.91.119.166

Name:   coltdb01-scan.example.com

Address: 10.91.119.168

[root@coltdb01 ~]# nslookup coltdb01-scan

Server:         10.91.119.134

Address:        10.91.119.134#53

Name:   coltdb01-scan.example.com

Address: 10.91.119.166

Name:   coltdb01-scan.example.com

Address: 10.91.119.168

Name:   coltdb01-scan.example.com

Address: 10.91.119.167