A method of performing communication between an Internet protocol (IP) address allocation server and an apparatus including a cable card and a host device is disclosed. In the communication method, the host acquires identification information of the cable card and transmits a message including the identification information of the cable card to the IP address allocation server. The host receives an IP address for the cable card from the IP address allocation server and sends the received IP address for the cable card to the cable card. Accordingly, it is possible to acquire the IP addresses for the host and the cable card via one physical interface. In addition, it is possible to stabilize an overall system by efficiently operating the IP process according to an operation mode of the cable card.