We are trying to use our second NIC card to allow external access to our database. We are experiencing "listener not found" errors. We tried several things. When we do not restrict by port number we are able to connect to the database. However if we only open port 1521 we can not. The database is created in "dedicated server mode". We have tried adding different port numbers that we thought that maybe we needed but we still end up with the error. Any suggestions.