Keep in mind that the Oracle listener gets involved only upon the initial connection request from a client to the DB. After the initial handoff of the client to the DB, the listener has NOTHING to do with the ongoing exchange between the 2. IMO, it make NO sense to have more than 1 listener for a single NIC. The NIC is a single threaded device. Only 1 packet at a time can be flowing through the NIC at a time. I see absolutely no advantage to have multiple Listeners servicing different ports on the same NIC, because only 1 listener at a time can be actively utilizing the NIC.