Methods and apparatus for determining, in a reliable manner, a port, physical location and/or device identifier, such as a MAC address, associated with a device using an IP address and for using such information, e.g., to support one or more security applications is described. Supported security applications include restricting access to services based on the location of a device seeking access to a service, determining the location of stolen devices, and verifying the location of the source of a message or other IP signal, e.g., to determine if a prisoner is contacting a monitoring service from a predetermined location.