The BGP tool is the source of truth for backbone waves — create and manage them here (Vader only shows a read-only status view). Lifecycle: planned → turning up (push JunOS with commit-confirmed) → live (eligible for the MPLS next-hop rewrite). Health is probed via the endpoint routers: interface + IS-IS adjacency + the DN-BACKBONE iBGP session. The iBGP session rides the wave loopback-to-loopback, so a fiber cut withdraws inter-POP prefixes by itself — a ZOMBIE state means the session survives without IS-IS (backup loopback reachability is defeating fail-closed: find and remove the static/BGP backdoor route).