The Shortest Path Bridging MAC (SPBM) network needs a mechanism to debug connectivity issues and to isolate faults. This is performed at Layer 2, not Layer 3. Connectivity Fault Management (CFM) operates at Layer 2 and provides an equivalent of ping and traceroute. To support troubleshooting of the SPBM cloud, the switch supports a subset of CFM functionality. Configure CFM on all SPBM VLANs.
CFM is based on the IEEE 802.1ag standard.
IEEE 802.1ag Connectivity Fault Management (CFM) provides OAM tools for the service layer, which allows you to monitor and troubleshoot an end-to-end Ethernet service instance. CFM is the standard for Layer 2 ping, Layer 2 traceroute, and the end-to-end connectivity check of the Ethernet network.
The 802.1ag feature divides or separates a network into administrative domains called Maintenance Domains (MD). Each MD is further subdivided into logical groupings called Maintenance Associations (MA). A single MD can contain several MAs.
Each MA is defined by a set of Maintenance Points (MP). An MP is a demarcation point on an interface that participates in CFM within an MD. Two types of MP exist:
Maintenance End Point (MEP)
Maintenance Intermediate Point (MIP)
CFM supports three kinds of standard CFM messages: Continuity Check Message (CCM), Loopback Message (LBM), and Linktrace Message (LTM). Messages are sent between Maintenance Points (MP) in the system.
On the switch, CFM is implemented using the LBM and LTM features only to debug SPBM. CCM messages are not required or supported.
You can assign maintenance levels for each CFM SPBM MEP and MIP to each SPBM B-VLAN individually or you can assign maintenance levels and global MEPs for all SPBM VLANs.