TNSNAMES.ORA order of IP addrsses

Question

I am using tnsnames.ora for my Oracle database connection. DB servers are clustered so tns names entry looks like:

ABCD = 
  (DESCRIPTION = 
    (ADDRESS_LIST = 
      (FAILOVER = on) 
      (LOAD_BALANCE = off) 
      (ADDRESS = (PROTOCOL = TCP)(HOST = 1.2.3.4)(PORT = 1521))
      (ADDRESS = (PROTOCOL = TCP)(HOST = 1.2.3.5)(PORT = 1521))
      (ADDRESS = (PROTOCOL = TCP)(HOST = 1.2.3.10)(PORT = 1521))
    ) 
    (CONNECT_DATA = 
      (SERVICE_NAME = abcd) 
      (FAILOVER_MODE = 
        (TYPE = SELECT) 
        (METHOD = BASIC) 
      ) 
   ) 
) 

Supposedly, if 1.2.3.4 does not respond, it is to failover and try 1.2.3.5, but it doesn't.

Even if 1.2.3.5 is online and .4 is offline, I get oracle connection error. When I change the order and put .5 on top, connection error goes away.

In web.config, connection string is defined as:

<add name="ABCDConnectionString" connectionString="Data Source=ABCD;User Id=my_id;Password=my_pwd;" providerName="Oracle.DataAccess.Client" />

Am I missing something when trying to use this tns names entry? I am pretty sure changing the order is not the solution as it defeats the purpose of having failover.