This read-only value identifies the interface of the uni-directional multicast send connection between the LEC and BUS, one row existing per client connected to the BUS. Because this is per-client, distinct from the BUS's own shared broadcast-out VC, it's the object to check when isolating whether one particular client's inbound path to the BUS, rather than the shared outbound distribution VC, is the source of a problem. One LEC client unable to have its broadcast traffic reach other clients on the ELAN, while all other clients work fine, points to a problem specific to this client's own send connection rather than the shared multicast-forward VC.