This read-only integer reports the next available VXLAN ID, in the range 0x0 to 0xFFFFFF, with the special value 0xFFFFFFFF indicating no ID is available to assign. Admins check this before creating a new VXLAN to know which ID the system would assign, or to detect that the VXLAN ID space is exhausted. For example, seeing 0xFFFFFFFF here would tell the admin all VXLAN IDs are in use and an existing VXLAN must be removed before a new one can be created.