This read-only INTEGER (1..255) specifies the virtual trunk identifier of the interface card associated with the trunk at the local node, where 1 through 254 denote a virtual trunk and 255 denotes a physical trunk. An administrator uses this to tell whether the row describes the physical port itself or one of several virtual trunks multiplexed over it. For example, a value of 255 tells the operator this trunk entry represents the underlying physical trunk rather than one of the logical virtual trunks riding on it.