Type 1 LSA known as router lsa in OSPF. It floods all the routers in an area and states the directly connected or interfaces of the router. LSA1 includes the link ID field that identifies the network number and subnet mask. Depending on type of link id has different meanings. Each router link is defined by one of the four types.
Type 1:- Point to Point to another router.
Link ID:- It is the neighbor router id.
Type 2:- This is tcommon to transient network.
Link ID:- Link ID is the address of the DR.
Type 3:- It is connection to stub network.
Link ID:- IP network or subnet number.
Type 4:- It represents virtual link.
Link ID:- It is the neighboring router id.
With this type 1 LSA defines router as ABR or an ASBR.
A refulgent explanation of LSA1