A、OSPF external LSAs are automatically flooded into all OSPF areas， unlike type 7 LSAs， which require that redistribution be configured.

B、External LSAs （type 5） are automatically changed to type 1 LSAs at ASBRs.

C、Type 5 LSAs are route summaries describing routes to networks outside the OSPF Autonomous System.

D、External network LSAs （type 5） redistributed from other routing protocols into OSPF are not permitted to flood into a stub area.