A communication apparatus to be used between first and second communication groups, each including one or more communication terminals, that perform communications by different types of communication protocols capable of embedding address information, comprises a first storage unit storing a destination address, and tunnel identification information for the first communication group when a packet transmitted from the second communication group is registered; a destination retrieval unit which determines whether a destination address extracted from the received packet is registered in the first storage unit; a second storage unit, storing information indicating whether the route designated by the tunnel identification information is constructible by a private address or by a global address; an encapsulation processing unit which extracts the address information for the first communication group from the destination address; and a control unit controlling whether the encapsulation is to be in accordance with the information of the second storage unit.