An Internet Protocol (IP) phone transmits on a network, an IP packet comprising a dynamically-assigned IP address. A computer associated with the network uses the dynamically-assigned IP address in the packet to identify a specific site to which the IP phone belongs and/or a specific local area network (LAN) to which the IP phone is connected. Then, data to be used to provide telephony service to the phone is recorded in a memory. In some embodiments, the computer associates the IP phone with a dialing plan unique to the specific site, wherein the dialing plan includes an area code to be used by the IP phone.