Setting Up Loopback Messages

Updated on 09 Aug 2024
3 Minutes to read
Contributors

Article summary

Did you find this summary helpful?

Thank you for your feedback

Loopback messages are unicast frames transmitted by a MEP. Sending a high volume of loopback messages can test the bandwidth, reliability or jitter of a service. A MEP can send a loopback to any MEP or MIP in the service. Loopback messages are discussed in IEEE 802.1ag.

To start the loopback messages

Access the page SOAM ▶CFM ▶MEP ▶LBM.
All existing loopback messages for Maintenance association End Points are displayed.
Click the MEPID of the MEP for which you want to start the LBM.
Complete the required fields, then click Start.

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

MEP Loopback (SOAM ▶CFM ▶MEP ▶LBM)

Parameter	Description
MEP Index Index	Index assigned to the Maintenance association End Point.
MEPID	Maintenance association End Point Identifier.
Active	Indicates whether a loopback request is active for that MEP.
Target Type	Loopback target by remote MEPID or MAC address.
Remote MEPID	Target remote MEPID. The remote MEP MAC address is resolved into the local MEP database.
MAC Address	Target MAC address. Only Unicast MAC address are valid for link trace target address.
VLAN Priority	Indicates how to determine the LBM VLAN priority value: CCM Priority: Use the same priority that MEP CCMs. Specific: Use a specific value specified by the Priority field.
Priority	The value assigned to the LBM VLAN priority. Range: 0–7
VLAN Drop Eligibility	Value for LBM VLAN drop eligibility bit. Checking this box sets the DEI bit to 1.
Nbr Message	Number of LBMs to send.
Interval	The interval, expressed in milliseconds, between LBMs. Range: 100–5000
Data TLV	Indicates whether LBMs should include a Data Type Length Value (TLV). Possible values are: None: No Data TLV included Incremental: A Data TLV with incremental byte values is included Pattern: A Data TLV based on a user data pattern is included.
Length	Amount of data, expressed in bytes, inside the data TLV. Range: 1–1488 bytes
Pattern	User data pattern for the Data TLV. Format: ASCII characters

Bottom of Table

Parameter	Description
Loopback Request	Indicates whether a loopback request is active or inactive for that MEP.
Target MAC Address	The target MAC address used for the latest loopback request.
Latest Start Time	The time the latest loopback request was initiated for that MEP.
Latest End Time	The time the latest loopback request has completed or was stopped for that MEP.
Next Seq. #	The sequence number for the next LBM initiated from that MEP.
Nbr LBM Requested LBM Requested	The number of LBM requested for the latest loopback request.
Nbr LBM Sent	The number of LBM sent for the latest loopback request. When the loopback is not active, this number should be the same as the number of LBM requested. If not, this implies the loopback request was stopped by a management command.
Nbr LBR Received LBM Received	The number of loopback replies (LBR) received for the latest loopback request.
LBR with Bad MSDU	The number of LBR received with a content that did not match the corresponding LBM for the latest loopback request.
Nbr LBR Duplicated	The number of LBR received with a sequence number already received for the latest loopback request.
Packet loss ratio	The computed packet loss ratio for the latest loopback request.
Nbr Packets Lost	The number of missing LBR for the latest loopback request.
Nbr Gaps	The number of times a sequence of LBRs went missing during the latest loopback request.
Largest Gap Size	The longest uninterrupted sequence of missing packets that was detected during the most recent loopback request.
Nbr LBR Out of Order	The number of times an LBR was received during the latest loopback request whose sequence number did not match the expected value.

Viewing Loopback Message Information

To view the loopback message information

Access the page SOAM ▶CFM ▶MEP ▶LBM.
Click the MEPID of the MEP for which you want to view LBM information.

For more information on specific parameters, refer to the "MEP Loopback (SOAM ▶CFM ▶ MEP ▶LBM)" table.

© 2024 Cisco and/or its affiliates. All rights reserved.

For more information about trademarks, please visit: Cisco trademarks
For more information about legal terms, please visit: Cisco legal terms
For legal information about Accedian Skylight products, please visit: Accedian legal terms and tradmarks

Was this article helpful?

What's Next

Setting Up Delay Measurements