A method performed in a core network of a cellular communications system for mapping a multicast Medium Access Control, MAC, address to a particular Protocol Data Unit, PDU, session, comprising: • at a User Plane Function, UPF,: ∘ obtaining (Fig. 5, step 2) multicast MAC address information comprising: ▪ a multicast MAC address to be used on a particular PDU session; and ▪ information that identifies a User Equipment, UE, associated with the particular PDU session, wherein the UPF is coupled to an Ethernet network via a switch, and wherein the switch is non-co-located with the UPF and obtaining (Fig. 5, step 2) the multicast MAC address information comprises obtaining (Fig. 5, step 2) the multicast MAC address information from the switch by receiving (Fig. 5, step 2) a control message comprising the multicast MAC address information, or wherein the switch is co-located with the UPF and obtaining (Fig. 5, step 2) the multicast MAC address information comprises obtaining (Fig. 5, step 2) the multicast MAC address information from the switch; and ∘ reporting (Fig. 5, step 3), to a Session Management Function, SMF, in the core network, use of the multicast MAC address on the particular PDU session; and • at the SMF: ∘ receiving (Fig. 5, step 3), from the UPF, the report of the use of the multicast MAC address on the particular PDU session, the report comprising the multicast MAC address to be used on the particular PDU session; and using (Fig. 5, step 5) the multicast MAC address to perform one or more operational tasks. • at a User Plane Function, UPF,: ∘ obtaining (Fig. 5, step 2) multicast MAC address information comprising: ▪ a multicast MAC address to be used on a particular PDU session; and ▪ information that identifies a User Equipment, UE, associated with the particular PDU session, wherein the UPF is coupled to an Ethernet network via a switch, and wherein the switch is non-co-located with the UPF and obtaining (Fig. 5, step 2) the multicast MAC address information comprises obtaining (Fig. 5, step 2) the multicast MAC address information from the switch by receiving (Fig. 5, step 2) a control message comprising the multicast MAC address information, or wherein the switch is co-located with the UPF and obtaining (Fig. 5, step 2) the multicast MAC address information comprises obtaining (Fig. 5, step 2) the multicast MAC address information from the switch; and ∘ reporting (Fig. 5, step 3), to a Session Management Function, SMF, in the core network, use of the multicast MAC address on the particular PDU session; and ∘ obtaining (Fig. 5, step 2) multicast MAC address information comprising: ▪ a multicast MAC address to be used on a particular PDU session; and ▪ information that identifies a User Equipment, UE, associated with the particular PDU session, wherein the UPF is coupled to an Ethernet network via a switch, and wherein the switch is non-co-located with the UPF and obtaining (Fig. 5, step 2) the multicast MAC address information comprises obtaining (Fig. 5, step 2) the multicast MAC address information from the switch by receiving (Fig. 5, step 2) a control message comprising the multicast MAC address information, or wherein the switch is co-located with the UPF and obtaining (Fig. 5, step 2) the multicast MAC address information comprises obtaining (Fig. 5, step 2) the multicast MAC address information from the switch; and ▪ a multicast MAC address to be used on a particular PDU session; and ▪ information that identifies a User Equipment, UE, associated with the particular PDU session, wherein the UPF is coupled to an Ethernet network via a switch, and wherein the switch is non-co-located with the UPF and obtaining (Fig. 5, step 2) the multicast MAC address information comprises obtaining (Fig. 5, step 2) the multicast MAC address information from the switch by receiving (Fig. 5, step 2) a control message comprising the multicast MAC address information, or wherein the switch is co-located with the UPF and obtaining (Fig. 5, step 2) the multicast MAC address information comprises obtaining (Fig. 5, step 2) the multicast MAC address information from the switch; and ∘ reporting (Fig. 5, step 3), to a Session Management Function, SMF, in the core network, use of the multicast MAC address on the particular PDU session; and • at the SMF: ∘ receiving (Fig. 5, step 3), from the UPF, the report of the use of the multicast MAC address on the particular PDU session, the report comprising the multicast MAC address to be used on the particular PDU session; and using (Fig. 5, step 5) the multicast MAC address to perform one or more operational tasks. ∘ receiving (Fig. 5, step 3), from the UPF, the report of the use of the multicast MAC address on the particular PDU session, the report comprising the multicast MAC address to be used on the particular PDU session; and using (Fig. 5, step 5) the multicast MAC address to perform one or more operational tasks.