scan listeners are not working

 Hi

scan listeners are not working oracle 11gr2  and windows server 2008 64bit. how to resolve this issues

ip address

172.17.3.21

172.17.3.22

172.17.3.23

 

C:\oracle_media\grid>runcluvfy.bat comp scan -verbose

 

Verifying scan

 

Checking Single Client Access Name (SCAN)...

  SCAN Name         Node          Running?      ListenerName  Port          Running?

  ----------------  ------------  ------------  ------------  ------------  ------------

  winrac-scan       winrac1       true          LISTENER_SCAN1  1521          true

  winrac-scan       winrac2       true          LISTENER_SCAN2  1521          true

 winrac-scan       unknown       true          LISTENER_SCAN3  1521          false

 

ERROR:

PRVF-5056 : Scan Listener "LISTENER_SCAN3" not running

 

Verification of SCAN VIP and Listener setup failed

 

Verification of scan was unsuccessful on all the specified nodes.