Setting Up Link Trace Messages

  • Published on Aug 9, 2024
  • 2 minute(s) read
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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 â–¶CFM â–¶MEP â–¶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 table.

MEP Link Trace (SOAM â–¶CFM â–¶MEP â–¶LTM)

Parameter Description
MEP 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 MEP.
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.

Viewing Link Trace Messages Information

To view the link trace message information

  1. Access the page SOAM â–¶CFM â–¶MEP â–¶LTM.

  2. Click the MEPID of the MEP for which you want to view LTM information.

For more information on specific parameters, refer to the "MEP Link Trace (SOAM â–¶CFM â–¶ MEP â–¶LTM)" table.

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