A method of Multi-Tone Mask (MTM) mode communications in a PLC network including a first router associated with a plurality of nodes. A super-frame spanning a time period is received within the subnetwork. The super-frame includes beacon frames in beacon slots within a beacon period, with each beacon frame in one of N TMs, a contention access period (CAP) including a plurality of CAP slots provided for each TM, and a poll-based contention-free period (CFP). The beacon frames provide time assignments within the super-frame including time assignments for the CAP slots and for the CFP, and TM assignments for the TMs in the CAP slots. One of nodes, another router in the subnetwork, or a router in another subnetwork transmits a broadcast frame on the PLC channel. The first router forwards the broadcast frame on the PLC channel in each of the N TMs within the time period.