Architecture for maintaining connection state of network address translation (NAT) devices by employing an out-of-band (OOB) technique externally to application connections without imposing additional requirements on the underlying native application(s). The OOB solution can be applied to arbitrary connections without requiring modification to an application protocol and works with TCP and UDP. A keep-alive (KA) application is employed as an OOB mechanism that injects KA packets that appear to the NAT device to be coming from the native connection. These injected packets fool the NAT device into resetting the inactivity timer for that connection, but do not fool or confuse the native application, which is oblivious to the spoofing. Accordingly, the connection will not terminate due to NAT timeouts, and therefore, a client/server protocol, for example, will not need to generate fake activity packets to keep the connection alive.