(Optional) Configuring LB for an LSP

This section describes how to configure loopback (LB) to monitor the connectivity of MPLS-TP links.

Context

LB is the most common tool that monitors the connectivity between MEPs or between a MEP and a MIP. Unlike CC or CV that is performed periodically, LB is performed at a time.

Commands can be run to trigger LB, and LB packets are used to check the following information:

Availability of a remote device
Round-trip delay in communication between MEPs
Loss of ping packets

Both the loopback function enabled using the ping meg command and CC enabled using the cc enable command are used to monitor the connectivity of bidirectional links. The following table describes differences between them.

**Table 1** Differences between loopback and CC
Item	Loopback enabled using the ping meg command	CC enabled using the cc enable command
Configuration procedure	To enable loopback, perform the following step: Run the ping meg command on a MEP to enable loopback and display statistics in real time.	To enable CC, perform the following steps: (Optional) Run the cc interval command to set an interval at which CCMs are sent on a MEP and its RMEP. (Optional) Run the cc exp command to set a priority for CCMs on the MEP and its RMEP. Run the cc send enable command to enable the MEP and its RMEP to send CCMs. Run the cc receive enable command to enable the MEP and its RMEP to receive CCMs.
Statistics display	The ping meg command displays statistics on the MEP.	An alarm is generated and reported if a connectivity fault between the MEP and its RMEP occurs.
Detection method	On-demand monitoring: monitors connectivity of a MEG at a time.	Proactive monitoring: periodically monitors connectivity of a MEG.
Detection object	MEP or MIP	MEP

Procedure

Run ping meg meg-name [ { mip ttl ttl-number { mip-id mip-id-value | node-id node-id value } [ if-num if-numvalue ] } | -c count-value | packet-size size-value | -t timeout-value ] ^* [ request-tlv ]
LB is enabled to monitor the connectivity of an MPLS-TP link.

The timeout-value parameter specifies a period for waiting for a response packet.

If the network speed is slow, set the timeout-value parameter to a large value in the ping meg command.