In one embodiment, bridges in a computer network maintain a per-port mapping table for each of its ports, where each mapping table maps, for each virtual connection (of more than 4K) at a respective port, i) frame encapsulation fields that uniquely identify a particular virtual connection at the respective port to ii) a particular multiple spanning tree (MST) instance. The bridges may then compute a checksum of a particular mapping table for a particular port, and share the checksum with a corresponding port interconnected with the particular port (e.g., of another bridge). Upon determining that the mapping tables at the corresponding ports match in response to the checksums matching, frames may then be forwarded between the ports based on the particular mapping table.