As shown in the figure, all routers advertise their directly connected OSPF-enabled links in a type 1 LSA and forward their network information to OSPF neighbors. The LSA contains a list of the directly connected interfaces, link types, and link states.

Type 1 LSAs are also referred to as router link entries.

Type 1 LSAs are flooded only within the area in which they originated. ABRs subsequently advertise the networks learned from the type 1 LSAs to other areas as type 3 LSAs.

The type 1 LSA link ID is identified by the router ID of the originating router.