see the test

SQL> create database link test using 'intdb';

Database link created.

SQL> select count(*) from BBLTX160@test;

COUNT(*)
----------
479

If u are able to connect to the remote server with username then check the global_names parameter on the remote server and make to 'False'.Now u should be able to use the database link from the workstation on which u have the authorization.
So its not the problem with database link it is a problem with firewall permission.