A method comprising the steps of: assigning a local source address to a mobile station in a telecommunication system, wherein the telecommunication system includes a home domain of the mobile station, a visited domain, and a multicast group that is identified by a multicast address, and wherein the local source address is to be used as a source address by the mobile station when the mobile station is sending a packet to the multicast address and is in the home domain; assigning a home address to the mobile station, wherein the home address is different from the local source address; detecting a current domain of the mobile station wherein the current domain is only one of the home domain and the visited domain and wherein the current domain is detected using a subnet identifier that identifies the current domain; comparing the current domain of the mobile station with a previous domain of the mobile station to generate a comparison result, wherein the previous domain is only one of the home domain and the visited domain; and switching, as a function of the comparison result, between using the local source address and using the home address as a source address when sending a packet from the mobile station to the multicast address for communicating with the multicast group, wherein: (i) the local source address is used as the source address for the packet, when the current domain is the home domain; and (ii) the home address is used as the source address for the packet, when the current domain is the visited domain. assigning a local source address to a mobile station in a telecommunication system, wherein the telecommunication system includes a home domain of the mobile station, a visited domain, and a multicast group that is identified by a multicast address, and wherein the local source address is to be used as a source address by the mobile station when the mobile station is sending a packet to the multicast address and is in the home domain; assigning a home address to the mobile station, wherein the home address is different from the local source address; detecting a current domain of the mobile station wherein the current domain is only one of the home domain and the visited domain and wherein the current domain is detected using a subnet identifier that identifies the current domain; comparing the current domain of the mobile station with a previous domain of the mobile station to generate a comparison result, wherein the previous domain is only one of the home domain and the visited domain; and switching, as a function of the comparison result, between using the local source address and using the home address as a source address when sending a packet from the mobile station to the multicast address for communicating with the multicast group, wherein: (i) the local source address is used as the source address for the packet, when the current domain is the home domain; and (ii) the home address is used as the source address for the packet, when the current domain is the visited domain. (i) the local source address is used as the source address for the packet, when the current domain is the home domain; and (ii) the home address is used as the source address for the packet, when the current domain is the visited domain.