The OSPF Domain ID value. The OSPF Domain ID value is a BGP extended community attribute value. It consists of a 2 byte Type field followed by a 6 byte Value field. The Type field value determines the Value field format. For an OSPF Domain ID the combined format of the Type and Value fields must be one of the following: - 00 05 {2 byte AS number} {4 byte local value} - 01 05 {4 byte IPv4 address} {2 byte local value} - 02 05 {4 byte AS number} {2 byte local value} In addition, Type 80 05 is equivalent to Type 00 05 and is allowed for back-compatibility. If the Value field is 00 00 00 00 00 00 then the value represents the NULL OSPF Domain ID. Use of a NULL OSPF Domain ID is only allowed for the primary OSPF Domain ID and only if there are no secondary OSPF Domain IDs.