The CFM Loopback Protocol

The loopback protocol sends loopback messages (LBM) to either a specified maintenance end-point (MEP) or to an MP MAC address. The CFM loopback protocol is similar to IP ICMP ping. The CFM loopback protocol displays whether there is connectivity between the initiating device and the target device. If an operational path to the MEP or MIP exists, the remote MEP or MIP will respond. If no response is received by the source MEP, no operational path exists. If no response is received use the linktrace protocol (The CFM Linktrace Protocol) to help verify where in the path the problem occurred.

If you specify a MEP, the specified remote MEP must have already communicated with this MEP and there must be an entry in the MEP database for the remote MEP. The loopback will fail if the remote MEP is specified and the specified MEP has not yet communicated with this MEP.

The LBM 802.1p priority can be configured when initiating a loopback.

This example shows how to send 5 loopback messages to MAC address 01:3a:b2:af:65:de from the myMA1 MEP 1000:

System(rw-config)->cfm md string-name myMD1
System(su-config-cfm-md.1)->ma string-name myMA1
System(su-config-cfm-ma.1)->mep 1000
System(su-config-cfm-mep.1000)->loopback mac 01:3a:b2:af:65:de messages 5
Sending 5 Ethernet CFM loopback messages to 01-3a-b2-af-65-de
...
Success rate is 100 percent (5/5)
System(su-config-cfm-mep.1000)->