SCAN IP address in 11gR2 RAC

SCAN in RAC

Single Client Access Name (SCAN) eliminates the need to change TNSNAMES entry when nodes are added to or removed from the Cluster. RAC instances register to SCAN listeners as remote listeners. Oracle recommends assigning 3 addresses to SCAN, which will create 3 SCAN listeners, though the cluster has got dozens of nodes.. SCAN is a domain name registered to at least one and up to three IP addresses, either in DNS (Domain Name Service) or GNS (Grid Naming Service). The SCAN must resolve to at least one address on the public network. For high availability and scalability, Oracle recommends configuring the SCAN to resolve to three addresses.
http://www.freeoraclehelp.com/2011/12/scan-setup-for-oracle-11g-release211gr2.html

How to start SCAN and SCAN Listener:
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#$GRID_HOME/bin/srvctl start scan
#$GRID_HOME/bin/srvctl start scan_listener

How to STOP the SCAN LISTENER and the SCAN VIP resources:
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#$GRID_HOME/bin/srvctl stop scan_listener
#$GRID_HOME/bin/srvctl stop scan

How to check the STATUS of the SCAN LISTENER and the SCAN VIP resources:
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#$GRID_HOME/bin/srvctl status scan_listener
SCAN listener LISTENER_SCAN1 is enabled
SCAN listener LISTENER_SCAN1 is not running
SCAN listener LISTENER_SCAN2 is enabled
SCAN listener LISTENER_SCAN2 is not running
SCAN listener LISTENER_SCAN3 is enabled
SCAN listener LISTENER_SCAN3 is not running

#$GRID_HOME/bin/srvctl status scan
SCAN VIP scan1 is enabled
SCAN VIP scan1 is not running
SCAN VIP scan2 is enabled
SCAN VIP scan2 is not running
SCAN VIP scan3 is enabled
SCAN VIP scan3 is not running

How to check SCAN-VIP in the resource file:
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#$GRID_HOME/bin/srvctl config scan
SCAN name:rac-scan,Network: 1/10.100.10.0/255.255.255.0/eth1
SCAN VIP name: scan1, /rac-scan.localdomain.com/10.1000.10.21
SCAN VIP name: scan1, /rac-scan.localdomain.com/10.1000.10.22
SCAN VIP name: scan1, /rac-scan.localdomain.com/10.1000.10.23

How to check SCN IP address on DNS:
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$nslookup <scan-name>

$nslookup rac-scan.localdomain.com
Server: dns.localdomain.com
Address: 10.100.10.70#53

Name:rac-scan.localdomain.com
Address: 10.100.10.23
Name:rac-scan.localdomain.com
Address: 10.100.10.22
Name:rac-scan.localdomain.com
Address: 10.100.10.21