4.6.6 Confirming the DNS Configuration for SCAN

Use the nslookup command to confirm that the DNS is correctly associating the SCAN with the addresses.

The following example shows how to use the nslookup command to confirm that the DNS is correctly associating the SCAN with the addresses:

root@node1]$ nslookup mycluster-scan
Server:         dns.example.com
Address:        192.0.2.001
 
Name:   mycluster-scan.example.com
Address: 192.0.2.201
Name:   mycluster-scan.example.com
Address: 192.0.2.202
Name:   mycluster-scan.example.com
Address: 192.0.2.203

After installation, when a client sends a request to the cluster, the Oracle Clusterware SCAN listeners redirect client requests to servers in the cluster.

Oracle strongly recommends that you do not configure SCAN VIP addresses in the hosts file. Use DNS resolution for SCAN VIPs. If you use the hosts file to resolve SCANs, then the SCAN can resolve to one IP address only.

Configuring SCANs in a DNS or a hosts file is the only supported configuration. Configuring SCANs in a Network Information Service (NIS) is not supported.