Method and apparatus for integration of network address translation and source address security, including, but not limited to, determining whether a gateway computer is integrated for network address translation and source address security, is described. A client computer requests a first address from the gateway computer and then requests a second address from the gateway computer. The latter request is done with a different client identifier that is nearly equivalent, except for one bit, to the client identifier used for the prior address request. If the gateway computer is integrated for network address translation and source address security, in response to the latter request a public address will be provided from the gateway computer to the client computer.