Edge-Core ECS4810-12M Layer 2 Management Manual page 451

distinguished by the domain name, maintenance level, maintenance
association's name, and assigned VLAN.
Basic CFM Operations
CFM uses standard Ethernet frames for sending protocol messages. Both
the source and destination address for these messages are based on
unicast or multicast MAC addresses, and therefore confined to a single
Layer 2 CFM service VLAN. For this reason, the transmission, forwarding,
and processing of CFM frames is performed by bridges, not routers.
Bridges that do not recognize CFM messages forward them as normal data.
There are three basic types of CFM messages, including continuity check,
link trace, and loop back.
Continuity check messages (CCMs) are multicast within a single Service
Instance (i.e., a specific MA), allowing MEPs to discover other MEPs within
the same MA, and MIPs to discover MEPs. Connectivity faults are indicated
when a known MEP stops sending CCMs, or a remote MEP configured in a
static list does not come up. Configuration errors, such as a cross-connect
between different MAs, are indicated when a CCM is received with an
incorrect MA identifier or maintenance level.
Loop back messages are used for fault verification. These messages can be
sent using the MAC address of any destination MEP within the same MA. If
the target MEP's identifier has been discovered through CCM messages,
then a loop back message can also be sent using the MEPs identifier. A
reply indicates that the destination is reachable.
Link trace messages are used for fault verification. These messages are
multicast frames sent out to track the hop-by-hop path to a target MEP
within the same MA. Responses provide information on the ingress, egress,
and relay action taken at each hop along the path, providing vital
information about connectivity problems. Responses allow the sender to
discover all of the maintenance points that would be traversed by a data
frame sent to the target MAC address.
SNMP traps can also be configured to provide an automated method of
fault notification. If the fault notification generator detects one or more
defects within the configured time period, and fault alarms are enabled, a
corresponding trap will be sent. No further fault alarms are sent until the
fault notification generator has been reset by the passage of a configured
time period without detecting any further faults. Upon receiving a fault
alarm, you should inspect the related SNMP objects for the reporting MEP,
diagnose the fault, correct it, and re-examine the MEP's SNMP objects to
see whether the fault notification generator has been reset.
Configuration Guidelines
Configure the maintenance domains with the MD List (see
1.
CFM Maintenance Domains").
Configure the maintenance associations with MA List (see
2.
CFM Maintenance Associations").
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Connectivity Fault Management
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