Device Level Underlay Topology Health

Learn about health of a device level underlay topology.

An ESTABILISHED underlay session state is considered as a Green (Healthy) state.
When the underlay session state of all the BGP neighbors is in ESTABLISHED state, the underlay topology health is Green (Healthy).
When a BGP neighbor (between the two devices) is not in ESTABLISHED state, the underlay topology health is Red (Degraded).
When all the neighbors between the devices are down, the underlay topology health is Black (Critical).

The following table describes device level underlay health based on BGP neighbors and underlay session state:


Device	Remote Device	BGP Neighbor Configured on Device Pointing to Remote Device	Underlay Session State	Device Underlay Health
Device1	Device2	Neighbor1	ESTAB	Green
	Device2	Neighbor2	ESTAB
	Device3	Neighbor3	ESTAB
	Device3	Neighbor4	ESTAB
Device 4	Device5	Neighbor5	CONN	Red
	Device5	Neighbor6	ESTAB
	Device6	Neighbor7	ESTAB
	Device6	Neighbor8	ESTAB
Device7	Device8	Neighbor10	CONN	Black
	Device8	Neighbor11	CONN
	Device9	Neighbor12	ESTAB