ETH-CFM relies on Ethernet addressing and reachability. ETH-CFM destination addressing may be derived from the Ethernet encapsulation, or may be a target address within the ETH-CFM PDU. Addressing is the key to identifying both the source and the destination management points (MPs).
The SR OS implementation dynamically assigns the MP MAC address using the appropriate pool of available hardware addresses on the network element, which simplifies the configuration and maintenance of the MP. The MP MAC address is tied to the specific hardware element, and its addressing can change when the associated hardware is changed.
The optional mac-address mac-address configuration command can be used to eliminate the dynamic nature of the MEP MAC addressing. This optional configuration associates a configured MAC address with the MEP in place of dynamic hardware addressing. The optional mac-address configuration is not supported for all service types.
ETH-CFM tests can adapt to changing destination MAC addressing by using the remote-mepid mep-id command in place of the unicast statically-configured MAC address. SR OS maintains a learned remote MAC table (visible by using the show>eth-cfm>learned-remote-mac command) for all MEPs that are configured to use ETH-CC messaging. Usually, when the remote-mepid mep-id command is used as part of a supported test function, the test searches the learned remote MAC table for a unicast address that associates the local MEP and the requested remote MEP ID. If a unicast destination address is found for that relationship, it is used as the unicast destination MAC address.
The learned remote MAC table is updated and maintained by the ETH-CC messaging process. When an address is learned and recorded in the table, it is maintained even if the remote peer times out or the local MEP is shut down. The address is not maintained in the table if the remote-mepid statement is removed from the associated context by using the no remote-mepid mep-id command for a peer. The CCM database clears the peer MAC address and enters an all-0 MAC address for the entry when the peer times out. The learned remote MAC table maintains the previously learned peer MAC address. If an entry must be deleted from the learned remote MAC table, the clear>learned-remote-mac [mep mep-id [remote-mepid mep-id]] domain md-index association ma-index command can be used. Deleting a local MEP removes the local MEP and all remote peer relationships, including the addresses previously stored in the learned remote MAC table.
The individual ETH-CFM test scheduling functions that use the remote-mepid mep-id option have slightly different operational behaviors.
Global interactive CFM tests support the remote-mepid mep-id option as an alternative to mac-address. A test only starts if a learned remote MAC table contains a unicast MAC address for the remote peer, and runs to completion with that MAC address. If the table does not contain the required unicast entry associated with the specified remote MEP ID, the test fails to start.
SAA ETH-CFM test types support the remote-mepid mep-id option as an alternative to mac-address. If, at the scheduled start of the individual run, the learned remote MAC table contains a unicast learned remote MAC address for the remote peer, the test runs to completion with the initial MAC address. If the table does not contain the required entry, the test terminates after the lesser window of either the full test run or 300 s. A run that cannot successfully determine a unicast MAC address designates the last test result as ‟failed”. If a test is configured with the continuous configuration option, it is rescheduled; otherwise, the test is not rescheduled.
OAM-PM Ethernet test families, specifically DMM, SLM, and LMM, support the remote-mepid mep-id option as an alternative to the dest-mac ieee-address configuration. If the learned remote MAC table contains a unicast learned remote MAC address for the remote peer, the test uses this MAC address as the destination. OAM-PM adapts to changes for MAC addressing during the measurement interval when the remote-mepid mep-id option is configured. It should be expected that the measurement interval includes update-induced PM errors during the transition. If the table does not contain the required entry, the test does not attempt to transmit test PDUs, and presents the ‟Dest Remote MEP Unknown” detectable transmission error.