This object, when on, enables leaking of routes from Level 2, the backbone, into Level 1, the area, on this instance. Administrators enable this so Level 1-only routers, which normally see only a default route toward the backbone, can instead learn specific inter-area routes for better path selection. For example, an engineer enables csIsisSysL2TO1Leak on an area border router to let Level 1 routers within the area choose the closest of two backbone exit points instead of blindly using a single default route.