Allied Telesis AT-S63 - Manual (Page 402)

Chapter 19: MLD Snooping
402 Section III: IGMP Snooping, MLD Snooping, and RRP Snooping
Port/Trunk ID
The port on the switch where the multicast router is connected. If the
switch learned the router on a port trunk, the trunk ID number, not the
port number, is displayed.
Router IP
The IP address of the multicast router.