A network node in a communication network, comprising: a plurality of ports (28A-28E), wherein at least two subsets (32A,32B) of the ports are grouped respectively into at least two LAG groups; and packet processing logic, which is coupled to receive data packets having respective destination addresses that specify forwarding the packets to groups of multiple recipients through at least one of the ports and to process the data packets so as to forward only a single copy of each of the data packets via the output ports in the subset, while distributing forwarded copies of the data packets among the output ports in the subset so as to balance a traffic load within the LAG group, wherein the packet processing logic is arranged to allocate to each of the received data packets a fabric multicast identification (FMID) value selected from, a range of possible FMID, values, each FMID being associated with one of the ports in the subset, and to forward the single copy to the port associated with the allocated FMID value, wherein the packet processing logic comprises multiple line cards connected to the ports and a switching fabric interconnecting the line cards, wherein, for each of the received data packets, a first line card connected to a first port via which the data packet is received is arranged to allocate the FMID value to the packet and to forward the packet to the switching fabric, and wherein the switching fabric and a second line card connected to a second port to which the data packet is to be sent are configured to forward the data packet responsively to the FMID value, wherein the first line card is arranged to assign to the data packets line card FMID (LC-FMID) values selected from a first range of possible LC-FMID values, and wherein the switching fabric is arranged to map the LC-FMID values to respective central FMID (C-FMID) values selected from a second range of possible C-FMID values that is smaller than the first range and to forward the data packets responsively to the C-FMID values, and, wherein the line cards are arranged to forward the data packets to the switching fabric without duplicating the data packets, and the switching fabric is configured to forward only one copy of each of the data packets to only one of the line cards (36B-36D) serving each of the subsets. a plurality of ports (28A-28E), wherein at least two subsets (32A,32B) of the ports are grouped respectively into at least two LAG groups; and packet processing logic, which is coupled to receive data packets having respective destination addresses that specify forwarding the packets to groups of multiple recipients through at least one of the ports and to process the data packets so as to forward only a single copy of each of the data packets via the output ports in the subset, while distributing forwarded copies of the data packets among the output ports in the subset so as to balance a traffic load within the LAG group, wherein the packet processing logic is arranged to allocate to each of the received data packets a fabric multicast identification (FMID) value selected from, a range of possible FMID, values, each FMID being associated with one of the ports in the subset, and to forward the single copy to the port associated with the allocated FMID value, wherein the packet processing logic comprises multiple line cards connected to the ports and a switching fabric interconnecting the line cards, wherein, for each of the received data packets, a first line card connected to a first port via which the data packet is received is arranged to allocate the FMID value to the packet and to forward the packet to the switching fabric, and wherein the switching fabric and a second line card connected to a second port to which the data packet is to be sent are configured to forward the data packet responsively to the FMID value, wherein the first line card is arranged to assign to the data packets line card FMID (LC-FMID) values selected from a first range of possible LC-FMID values, and wherein the switching fabric is arranged to map the LC-FMID values to respective central FMID (C-FMID) values selected from a second range of possible C-FMID values that is smaller than the first range and to forward the data packets responsively to the C-FMID values, and, wherein the line cards are arranged to forward the data packets to the switching fabric without duplicating the data packets, and the switching fabric is configured to forward only one copy of each of the data packets to only one of the line cards (36B-36D) serving each of the subsets.