The VPLS OAM toolset provides mechanisms for fault detection and diagnostics. For topology discovery, oam mac-trace is used to trace the path for a specific MAC address across the VPLS network, identifying the sequence of PEs and the ultimate egress point (SAP or SDP). This directly discovers the forwarding path.

The oam mac-populate command is also used for discovery. It advertises locally learned MAC addresses to all other PEs in the VPLS instance. By subsequently inspecting the Forwarding Databases (FDBs) on remote PEs, an operator can determine which PEs are active members of the service and have correctly learned the MACs, thereby discovering the VPLS service topology from a membership perspective.

A. oam mac-ping: This tool verifies reachability to a specific MAC address within the VPLS but does not trace the path or discover the network topology.

C. oamsvc-ping: This tool verifies the integrity and connectivity of the underlying service infrastructure (such as SDP bindings) between PEs, not the MAC-level forwarding topology.

1. Nokia 7750 SR OS Services Guide, Release 21.10.R1, "VPLS OAM" section.

Page 1008 (mac-trace): "The mac-trace OAM tool is used to discover the path from the ingress PE to the egress PE for a specific MAC address. The path is a list of Nokia 7750 SR nodes that the frame would traverse to reach the destination from the source." This explicitly defines mac-trace as a discovery tool.

Page 1008 (mac-populate): "The mac-populate OAM tool is used to populate the FDB of remote PE routers with the MAC addresses learned at the local PE router. This allows the remote PE routers to learn the MAC addresses before any data traffic is sent. This can be used to verify the VPLS service on the remote PE routers." This describes its function which, when combined with FDB inspection, serves as a topology discovery mechanism.

Page 1007 (mac-ping): "The mac-ping OAM tool is used to verify that a MAC address is learned by the VPLS service and displays the egress SAP or SDP on which the MAC is learned." This confirms its role as a verification, not discovery, tool.

2. Nokia Data Center and Cloud Networking (4A0-105) Student Guide, Module 4: Virtual Private LAN Service (VPLS).

Section: VPLS OAM: This section details the VPLS-specific OAM tools. It describes mac-trace for path discovery and mac-populate for populating remote FDBs, which is a key step in verifying and discovering the set of PEs participating in the service. It contrasts these with mac-ping, which is presented as a simple MAC reachability test.