Resolve the SCAN Issue while Installing Oracle Real Application Clusters 11g Release 2

ext, create a new shell script named /usr/bin/nslookup as shown below while
replacing 24.154.1.34 with your primary DNS, rac-scan with your
SCAN host name, and 192.168.56.91 with your SCAN IP address:
#!/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: racn-scan"
 echo "Address: 192.168.56.91 "
else
 /usr/bin/nslookup.original $HOSTNAME
fi
Finally, change the new nslookup shell script to executable:
[root@rac1 ~]# chmod 755 /usr/bin/nslookup
Remember to perform these actions on both Oracle RAC nodes.
The new nslookup shell script simply echo's back your SCAN IP address

whenever the CVU calls nslookup with your SCAN host name.