MEPs and MIPs filter CCMs from higher and lower domain levels as described in the following table.
Table 6. Continuity Check Message Processing
Frames at Frames from UP-MEP Action Down-MEP Action MIP Action
Less than my level Bridge-relay side or
Wire side
Drop Drop Drop
My level Bridge-relay side Consume Drop Add to MIP-DB and
forward
My level Wire side Drop Consume add to MIP-DB and
forward
Greater than my
level
Bridge-relay side or
Wire side
Forward Forward Forward
All the remote MEPs in the maintenance domain are defined on each MEP. Each MEP then expects a
periodic CCM from the configured list of MEPs. A connectivity failure is then defined as:
• Loss of three consecutive CCMs from any of the remote MEP, which indicates a network failure.
• Reception of a CCM with an incorrect CCM transmission interval, which indicates a configuration
error.
• Reception of a CCM with an incorrect MEP ID or MAID, which indicates a configuration or cross-
connect error. This error could happen when different VLANs are cross-connected due to a
configuration error.
• Reception of a CCM with an MD level lower than the receiving MEP, which indicates a configuration
or cross-connect error.
• Reception of a CCM containing a port status/interface status TLV, which indicates a failed bridge or
aggregated port.
The continuity check protocol sends fault notifications (Syslogs, and SNMP traps, if enabled) whenever
you encounter any of the these errors.
Enabling CCM
To enable CCM, use the following commands.
1. Enable CCM.
ECFM DOMAIN mode
no ccm disable
The default is Disabled.
2. Configure the transmit interval (mandatory). The interval specified applies to all MEPs in the domain.
ECFM DOMAIN mode
ccm transmit-interval seconds
The default is 10 seconds.
802.1ag
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