ZTE Corporation ZTE Corporation Cisco Systems Cisco Systems China mobile Each OSPF prefix can be advertised with an 8-bit field to indicate specific properties of that prefix. However, all the OSPFv3 Prefix Options bits have already been assigned and only a few bits remain unassigned in the flags field of the OSPFv2 Extended Prefix TLV. This document solves this problem by defining variable-length Prefix Attribute Flags sub-TLV for OSPF. This sub-TLV is applicable to OSPFv2 and OSPFv3.