How to Use Connectivity Fault Management in Your Network

The Connectivity Fault Management (CFM) process, as defined in the IEEE 802.1Q-2011 standard, provides network operators the means to monitor and troubleshoot services that may span multiple domain Ethernet networks. It provides a set of diagnostics and monitoring functions at the service provider level, allowing operators:

CFM allows a customer to validate the end-to-end Ethernet service within a single domain network, a large network that is segmented into separate domains within the same organization, or a network that has contracted with a service provider. In the event of a degradation of that service, CFM provides diagnostic data that can locate the problem within a single organization or that can be forwarded to the service provider. Whether working with an outside entity or within a single organization, CFM can:

The Extreme Networks S- K- and 7100-Series CFM implementation supports the monitoring of a VLAN service, and the association of one or more VLANs with the primary service. For the remaining discussion in this chapter, any reference to a CFM monitored service is a reference to a CFM monitored VLAN service. A CFM service is monitored by the periodic sending of continuity check messages (CCM) across the monitored service. A CCM is a multicast message, confined to a single operator domain that provides a means to detect connectivity failures or configuration errors for that monitored service. These messages are unidirectional and do not solicit a response. Each end of a CFM monitored service transmits a periodic multicast CCM inward towards the other end of the service. The primary service can both send and receive CCMs. Services associated with the primary can only receive CCMs.

A CFM monitored service resides within three hierarchical layers of CFM configuration:

Multiple services can be associated with the primary service by configuring a VLAN table for the primary service.

The CFM loopback protocol provides for connectivity verification by sending loopback messages between the initiating device and a MEP or a MAC address. The CFM linktrace protocol provides for path verification and helps identify where in the path a connectivity problem is located. Linktrace messages can be sent between the initiating device and a MEP or a MAC address. CFM can notify the network operator by Syslog or SNMP traps when connectivity failures or configuration errors are detected.

The minimum generated alarm defect can be set for both Syslogs and traps. See MEP Defect Definitions for reported defect details. Logging can be filtered by MD, MA, or MEP.

CFM configuration takes place within an hierarchy of configuration modes or contexts (see CFM Configuration Modes):