I have a laptop with Oracle 8.1.6 server and client installed on it, and I have one instance on the laptop called tst.

On our network, we have an AIX machine running Oracle 8.1.6 with several instances installed, one of which is prod.
With my laptop attached to the network, I can connect through SQL*PLUS, DBA Studio, Toad, etc. to my local instance (tst) and the AIX instances (prod). For example, right now, I have the local instance and two network instances open in Toad.

However, when I create a database link on my local instance to one of the network instances, using
create database link prod connect to <user>
identified by <pwd> using 'PROD.WORLD'
trying to access that link results in an Oracle error. The error says "ORA-02085: database link PROD connects to PROD.ABC.COM".

The prod above is *exactly* what it is in the TNSNAMES.ORA, and it is what I use to connect through SQL*PLUS, DBA Studio, etc. to the instance. The SQLNET.ORA has a
table.default_domain = 'WORLD'
in it. The TNSNAMES.ORA for the database is
(ADDRESS = (PROTOCOL = TCP)(HOST = a.b.c.d)(PORT = 1521))

The entry for tst looks identical, except the host address is my local machine name and the SID is tst. I can tnsping all databases fine. I have tried with this with several instances on the AIX machine, and none of them will work, even though I can connect to all of them.

Why would I be able to connect to the database, but be able to link to it? What else can I look at?