A method in accordance with the present invention comprises identifying a M-bit multicast address and deriving a N-bit PON port identifier from the M-bit multicast address. Identifying the M-bit multicast address and deriving the N-bit PON port identifier are performed at an Optical Line Terminal (OLT) of a Passive Optical Network (PON). The N-bit PON port identifier has fewer bits than the M-bit multicast address. Deriving the N-bit PON port identifier includes mapping N-1 Least Significant Bits (LSB) of the M-bit multicast address to N-1 LSB of the N-bit PON port identifier and setting a 1 Most Significant Bit (MSB) of the N-bit PON port identifier to a bit setting that designates the N-bit PON port identifier as being a multicast port identifier.