This read-write enum switches this TrBRF's IEEE Spanning Tree Protocol implementation between using the IBM bridge functional address (yes(2)) instead of the default IEEE functional address (no(1)) for its BPDU frames. This matters specifically for interoperability with older IBM source-route bridging equipment on the same Token Ring network that expects BPDUs addressed to the IBM functional address rather than the standard IEEE one. An admin integrating a legacy IBM bridge into a TrBRF where STP loops are being unexpectedly detected might try enabling this setting as part of matching the addressing scheme the older equipment expects.