Connecting to RAC using SQLDeveloper

The following are two definition in tnsnames.ora pointing to the same RAC database. The first one uses name (racora1),
the second (racora) uses actual IP address:

racora1 = (DESCRIPTION =  (ADDRESS_LIST =    (ADDRESS = (PROTOCOL = TCP)(HOST = db1.testoracle.COM)(PORT = 1521))    (ADDRESS = (PROTOCOL = TCP)(HOST = db2.testoracle.COM)(PORT = 1521))    (LOAD_BALANCE = yes)  )  (CONNECT_DATA =    (SERVER = DEDICATED)    (SERVICE_NAME = ORCL.testoracle.COM)    (FAILOVER_MODE =      (TYPE = SELECT)      (METHOD = BASIC)      (RETRIES = 180)      (DELAY = 5)    )  ))

racora2 = (DESCRIPTION =  (ADDRESS_LIST =    (ADDRESS = (PROTOCOL = TCP)(HOST = 192.155.1.1)(PORT = 1521))    (ADDRESS = (PROTOCOL = TCP)(HOST = 192.155.1.2)(PORT = 1521))    (LOAD_BALANCE = yes)  )  (CONNECT_DATA =    (SERVER = DEDICATED)    (SERVICE_NAME = ORCL.testoracle.COM)    (FAILOVER_MODE =      (TYPE = SELECT)      (METHOD = BASIC)      (RETRIES = 180)      (DELAY = 5)    )  ))

If you use SQL Developer to connect
to racora1 using the TNS, you will encounter the following error:
Status: Failure - Test failed: (null).

It works fine if you connect to racora. Apparently, it is not able to perform a nslookup to obtain the IP address when using TNS. It works fine if you use advance and use thin client to connect as in:
Strangely, if you use Advanced and put the following string, it works:
jdbc:oracle:thin:@(DESCRIPTION=(ADDRESS_LIST=(ADDRESS = (PROTOCOL = TCP)(HOST = db1.testoracle.COM)(PORT = 1521))(ADDRESS = (PROTOCOL = TCP)(HOST = db2.testoracle.COM)(PORT = 1521))(LOAD_BALANCE = yes))(CONNECT_DATA=(SERVER = DEDICATED)(SERVICE_NAME = ORCL.testoracle.COM)(FAILOVER_MODE=(TYPE = SELECT)(METHOD = BASIC)(RETRIES = 180)(DELAY = 5))))