Monitor one Ethernet link
IEEE 802.3ah introduced Ethernet link OAM as part of Ethernet in the First Mile. It operates between directly attached peers. During discovery the peers exchange OAM information, including capabilities supported at each end.
Link monitoring can report events such as an error threshold being exceeded. A peer can also signal remote fault conditions. When supported and permitted, remote loopback returns test traffic on the same link for diagnosis and can interrupt normal traffic.
Choose the scope of the diagnosis
Use link OAM to check the handoff or another individual Ethernet link. Use CFM to check continuity between Ethernet service endpoints. A healthy link OAM session at a customer handoff can coexist with a CFM defect when a fault interrupts the service deeper in the network.
Try it in a lab
- On a dedicated lab link with OAM-capable interfaces, enable link OAM with at least one end in active mode. Confirm that each end discovers its directly connected peer.
- If both peers allow remote loopback, enable it briefly and confirm test frames return on the same link. Clear loopback and verify normal traffic resumes.
- If the handoff is part of a separately monitored CFM service, interrupt an internal service path while keeping the handoff up. Compare the healthy handoff OAM discovery with the CFM continuity defect.