IS-IS LSPs contain information about the LSP itself in the attribute block of the LSP header, which is 8 bits long.

* P bitPartition repair bit, 8th bit, indicates if a partitioned Level 1 area can be repaired (joined) over Level 2 area. Modern deployments of IS-IS generally do not support partition repair, and will not set the P bit.
* ATT bitAttached bit, 7th-4th bits, indicates if the originating router is attached to another area.
** If these bits are set by the Level 1/Level 2 router in its Level 1 LSP, other routers