Multicast loopback also supports the new intervals (seeLoopback). However, the operator must be careful when using this approach. Every MEP in the association responds to this request. This means an exponential impact on system resources for large scale tests. If the multicast option is used and there with an interval of 1 (100ms) and there are 50 MEPs in the association, this results in a 50 times increase in the receive rate (500pps) compared to a unicast approach. Multicast displays are not be updated until the test is completed. There is no packet loss percentage calculated for multicast loopback commands.
This on demand operation tool is used to quickly check the reachability of all MEPs within an Association. A multicast address can be coded as the destination of an oam eth-cm loopback command. The specific class 1 multicast MAC address or the keyword ‟multicast” can be used as the destination for the loopback command. The class 1 ETH-CFM multicast address is in the format 01:80:C2:00:00:3x (where x = 0 - 7 and is the number of the domain level for the source MEP). When the ‟multicast” option is used, the class 1 multicast destination is built according to the local MEP level initiating the test.
Remote MEPs that receive the multicast loopback message, configured at the equivalent level, are terminated and process the multicast loopback message by responding with the appropriate unicast loopback response (ETH-LBR). Regardless of whether a multicast or unicast ETH-LBM is used, there is no provision in the standard LBR PDU to carry the MEP-ID of the responder. This means only the remote MEP MAC Address is reported and subsequently displayed. MIPs do not extract a multicast LBM request. The LBM multicast is transparent to the MIP.
MEP loopback stats are not updated as a result of this test being run. That means the received, out-of-order and bad-msdu counts are not affected by multicast loopback tests. The multicast loopback command is meant to provide immediate connectivity troubleshooting feedback for remote MEP reachability only.
oam eth-cfm loopback multicast mep 28 domain 14 association 2 interval 1 send-
count 100
Eth-Cfm Loopback Test Initiated: Mac-Address: multicast, out service: 5
MAC Address Receive Order
-------------------------------------------------------------------------------
00:00:00:00:00:30 1 2 3 4 5 6 7 8 9 10 11 12 13
14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47
48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 6
4 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80
81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97
98 99 100
00:00:00:00:00:32 1 2 3 4 5 6 7 8 9 10 11 12 13
14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47
48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 6
4 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80
81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97
98 99 100
Sent 100 multicast packets, received 200 packets