This read-only value identifies the VPI of the uni-directional multicast send connection between the LEC and BUS, paired with busClientMSendVci. Together these two identify the exact VC this individual LEC client uses to send broadcast, multicast, and unknown-destination traffic up to the BUS, the specific connection to capture or check when this one client's outbound broadcasts seem to not be reaching the rest of the emulated LAN. If this client's VPI shows no cell activity while the client claims to be sending address-resolution broadcasts, the fault lies in this specific client-to-BUS connection rather than in BUS distribution to other clients.