issue with dblink

I am creating a db link and this the error received
CREATE PUBLIC DATABASE LINK "test.domain"
CONNECT TO "testro" IDENTIFIED BY testro
USING 'linkdb';

if I try to select using the dblink, then following error is reported..

select count(*) from tab@test.domain;
select count(*) from tab@test.domain
                         *
ERROR at line 1:
ORA-02085: database link test.domain connects to
linkdb.domain

If I create the dblink using the IDENTIFIED BY VALUES (from password in user$), then while querying from dblink following ora-600 is reported

ERROR at line 1:
ORA-00600: internal error code, arguments: [kzdlk_zt2 err],
[18446744073709551603], [], [], [], [], [], [], [], [], [], []


what is the correct procedure/syntax to create db link? I am in 11.2.0.3