A computer network device (such as a switch or a router) that implement host tracking is described. During operation, the computer network device may receive a report message that is associated with a host, which indicates that the host wants to join a group in a network that receives an audio-video channel from a source. In response, the computer network device may add information associated with the host to a group data structure associated with one or more hosts in the group. Then, when the computer network device receives a leave message that is associated with the host, the computer network device may remove or deactivates the host from the group data structure. Moreover, when the group data structure is empty or has no active hosts, the computer network device may stop forwarding the audio-video channel from the source to the group without further delay.