This read-only value reports the Link State ID of a router-LSA, a type-specific field holding either a router ID or an IP address that identifies the piece of the routing domain the advertisement describes. An admin uses it, together with the router ID and area, to uniquely identify which router-LSA entry this row represents. For example, for a router-LSA the Link State ID typically matches the originating router's own router ID, letting the admin correlate this entry back to a specific router.