A loopback message is generated by an MEP to its peer MEP or a MIP (Figure: CFM loopback). The functions are similar to an IP ping to verify Ethernet connectivity between the nodes.
The following loopback-related functions are supported:
Loopback message functionality on an MEP or MIP can be enabled or disabled.
MEP supports generating loopback messages and responding to loopback messages with loopback reply messages. The ETH-LB PDU format does not allow a MEP to have more than a single active ETH-LB session.
MIP supports responding to loopback messages with loopback reply messages when loopback messages are targeted to self.
SenderID TLV may optionally be configured to carry the ChassisID. When configured, this information is included in LBM messages.
Only the ChassisID portion of the TLV is included.
The Management Domain and Management Address fields are not supported on transmission.
As per the specification, the LBR function copies and returns any TLVs received in the LBM message. This means that the LBR message includes the original SenderID TLV.
Supported for both service (id-permission) and facility MEPs (facility-id-permission).
Supported for both MEP and MIP.
Displays the loopback test results on the originating MEP.
The ETH-LBM (loopback) function includes parameters for sub second intervals, timeouts, and new padding parameters.
When an ETH-LBM command is issued using a sub second interval (100ms), the output success is represented with a ‟!” character, and a failure is represented with a ‟.” The updating of the display waits for the completion of the previous request before producing the next result. However, the packets maintain the transmission spacing based on the interval option specified in the command.
oam eth-cfm loopback 00:00:00:00:00:30 mep 28 domain 14 association 2 interval 1
send-count 100 timeout 1
Eth-Cfm Loopback Test Initiated: Mac-Address: 00:00:00:00:00:30, out service: 5
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!.!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!
Sent 100 packets, received 100 packets [0 out-of-order, 0 Bad Msdu]
Packet loss 1.00%
When the interval is one seconds or higher, the output provides information that includes the number of bytes (from the LBR), the source MEP ID (format md-index/ma-index/mepid), and the sequence number as it relates to this test and the result.
oam eth-cfm loopback 00:00:00:00:00:30 mep 28 domain 14 association 2 interval 10
send-count 10 timeout 1
Eth-Cfm Loopback Test Initiated: Mac-Address: 00:00:00:00:00:30, out service: 5
56 bytes from 14/2/28; lb_seq=1 passed
56 bytes from 14/2/28; lb_seq=2 passed
56 bytes from 14/2/28; lb_seq=3 passed
56 bytes from 14/2/28; lb_seq=4 passed
56 bytes from 14/2/28; lb_seq=5 passed
56 bytes from 14/2/28; lb_seq=6 passed
56 bytes from 14/2/28; lb_seq=7 passed
56 bytes from 14/2/28; lb_seq=8 passed
56 bytes from 14/2/28; lb_seq=9 passed
56 bytes from 14/2/28; lb_seq=10 passed
Sent 10 packets, received 10 packets [0 out-of-order, 0 Bad Msdu]
Packet loss 0.00%
Because ETH-LB does not support standard timestamps, no indication of delay is produced as these times are not representative of network delay.
By default, if no interval is included in the command, the default is back to back LBM transmissions. The maximum count for such a test is 5.