db link between 11G and 10G not working

 Hi,

I create a db_link from 11G ( 11.2.0.2 test database) to a 10G  ( 10.2.0.3) as sysdba, the databases are on physiccally seperate servers.

create public database link PROD using 'prod_server1';

And my tnsnames.ora is :

PROD_SERVER1 =
  (DESCRIPTION =
    (ADDRESS_LIST =
      (ADDRESS = (PROTOCOL = TCP)(HOST =server1)(PORT = 1521))
    )
    (CONNECT_DATA =
      (SERVER = DEDICATED)
      (SERVICE_NAME = PROD)
    )
  )

When I do a query on a small table using the db_link, the query hang there

select count(*) from tab1@prod;

And I don't see any db_link sessions on the PROD .

But I can connect to the PROD database from sqlplus

$sqlplus user1/pwd@prod_server1