This DisplayString object names the specific spanning-tree bridge instance associated with this VLAN, on devices that support multiple bridge instances under one SNMP agent. It lets a management application map a VLAN to the correct spanning-tree instance for topology and loop-prevention purposes; leaving it as a NULL string causes the device's default bridge to apply. On a switch running multiple per-VLAN spanning-tree instances, an admin might set vlanBridgeName to 'STP-Instance-2' to associate this VLAN's traffic with that bridge's spanning-tree calculations.