ORA-25408

THis is two node RAC 11gr2, with scan configured. Some web spplication users get ORA-25408 errors often recently.

But client (.net on ms windows server) tnsnames.ora still not chnaged to using scan.

prod.world =
(DESCRIPTION=
 (FAILOVER=ON)
 (LOAD_BALANCE=ON)
 (ADDRESS=
   (PROTOCOL=TCP) 

   (HOST=<ip address 1>)
   (PORT=1521))
 (ADDRESS=
   (PROTOCOL=TCP)
   (HOST==<ip address 2>)
)
   (PORT=1521))
 (CONNECT_DATA=
      (SERVICE_NAME=prod.world)
      (failover_mode=
          (type=session)
          (method=basic)
      )
  )
)

I just found that it uses ip address instead of host name.

Does any one have any suggestion?

Thank you!