This read-write enum lets an admin manually pin the spanning tree state, forwarding(2) or blocking(3), of this TrCRF's internal logical port, the one that connects the TrCRF up to its parent TrBRF, overriding the TrCRF's own spanning tree algorithm on just that internal link. This is a more targeted override than ciscoTsPortCfgSpanningTreeMode, which pins a physical port; here the admin is manually controlling the logical bridging relationship between a TrCRF and its TrBRF specifically. An admin isolating whether a TrCRF-to-TrBRF loop exists would force this internal port to blocking(3) as a diagnostic step rather than manipulating physical ports.