TCP/IP Guide

IP NAT Bidirectional (Two-Way/Inbound) Operation

Traditional NAT is designed to handle only outbound transactions; clients on the local network initiate requests and devices on the Internet and send back responses. However, in some circumstances, we may want to go in the opposite direction. That is, we may want to have a device on the outside network initiate a transaction with one on the inside. To permit this, we need a more capable type of NAT than the traditional version. This enhancement goes by various names, most commonly Bidirectional NAT, Two-Way NAT, and Inbound NAT. All of these convey the concept that this kind of NAT allows both the type of transaction you saw in the previous topic and also transactions initiated from the outside ...