Note:
An uplink port refers to an access port or LAG or hybrid port or LAG that is facing the network core.
A fault on the uplink port or LAG brings down all access ports with services independent of the encapsulation type of the access port (null, dot1q, or QinQ), that is, support Link Loss Forwarding (LLF). A fault propagated from the uplink port or LAG to access ports is based on configuration. A fault is propagated only in a single direction from the uplink port or LAG to access port.
A fault on the uplink port or LAG is detected using Loss of Signal (LoS) and EFM-OAM.
The following figure show local fault propagation.
Figure: Local fault propagation
