---
title: "Set Up Link Trace Messages"
slug: "setting-up-link-trace-messages"
tags: ["MEP", "CFM", "sensor control ", "linktrace", "Assurance Sensor Control"]
updated: 2026-07-07T14:09:30Z
published: 2022-02-25T20:18:52Z
canonical: "docs.crossworkassurance.cisco.com/setting-up-link-trace-messages"
---

> ## Documentation Index
> Fetch the complete documentation index at: https://docs.crossworkassurance.cisco.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Set Up Link Trace Messages

Link Trace Messages (LTM) are multicast frames transmitted by a MEP to track the path (hopby-hop) to a destination MEP. Each receiving MEP sends a trace route reply directly to the originating MEP, and regenerates the trace route message. LTM are discussed in IEEE 802.1ag.

**▶ To start the link trace messages**

1. Access the page **SOAM ▶ CFM ▶ MEP ▶ LTM**. All existing link trace information for Maintenance association End Points is displayed.
2. Click the **MEPID** of the MEP for which you want to start the LTM.
3. Complete the required fields, then click **Start**.

For more information on specific parameters, refer to the following tables.

**MEP Link Trace (SOAM ▶ CFM ▶ MEP ▶ LTM)**

| Parameter | Description |
| --- | --- |
| MEP Index Index | Index of the Maintenance association End Point |
| MEPID | Maintenance association End Point Identifier |
| Target Type | Link trace target by remote **MEPID** or **MAC address**. |
| Remote MEPID R-MEPID | Targeted remote MEPID. The remote MEP MAC address is resolved into the local MEP database. |
| LTR Received | The number of link trace responses received by this MEP |
| MAC Address | Target MAC address. Only unicast MAC addresses are valid for link trace target address. |
| TTL | Link trace time to live. Range: 0–255 If it is initially set to 0, no response should be received. |
| Set FDB Only Flag | Enables the LTM to set the flag "UseFDBonly" (IEEE 802.1ag) or the flag "HWonly" (Y.1731) |

**Bottom of Table**

| Parameter | Description |
| --- | --- |
| LTM Sequence Number Next Seq. # | Sequence number used by the latest link trace request initiated from that ME |
| Target MAC Address Target MAC | Target MAC address used by the latest link trace request |
| TTL | Link trace time to live received in link trace responses. |
| F | Forwarded. Indicates that the responder maintenance point did forward the LTM. |
| T | Terminal MEP. Indicates that the responder maintenance point is a MEP. |
| Action | Indicates how the responder system processes frames targeted for the destination address specified by the LTM Possible values are: - **RlyHit**: The LTM reached a maintenance point whose MAC address matches the target MAC address. - **RlyFDB**: The Egress Port was determined by consulting the Filtering Database. - **RlyMPDB**: The Egress Port was determined by consulting the MIP CCM Database. |
| TLV Type | Indicates which Type Length Values (TLVs) are included in link trace responses |
| TLV Value | The TLV values included in link trace responses |

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