This read-only INTEGER (1-1024) is the unique identifier for a TrCRF entry, and the description notes it doubles as the index into the vtpVLANEntry table in the separate Cisco VTP MIB, meaning this number is the join key between Token Ring-specific configuration here and the switch's general VLAN database. An admin cross-referencing a TrCRF's Token Ring settings, like its spanning tree timers elsewhere in this table, with its VLAN identity in VTP would use this shared number to connect the two MIBs' views of the same logical network. A TrCRF numbered 100 in this table corresponds exactly to VLAN 100 in the VTP MIB.