2-88
Cisco ONS 15310-CL and Cisco ONS 15310-MA Troubleshooting Guide, R7.0
Chapter2 Alarm Troubleshooting
2.7.135 LOF (OCN)
The EC1-1 LOF alarm occurs when a port on the reporting EC-1 port has an LOF condition. LOF
indicates that the receiving ONS 15310-CL or ONS 15310-MA has lost frame delineation in the
incoming data. LOF occurs when the SONET overhead loses a valid framing pattern for 3 milliseconds.
Receiving two consecutive valid A1/A2 framing patterns clears the alarm.

Clear the LOF (EC1) Alarm

Step1 Verify cabling continuity to the port reporting the alarm. To verify cable continuity, follow site practices.
Caution Always use the supplied electrostatic discharge wristband when working with a powered ONS15310-CL
or ONS 15310-MA.
Step2 If cabling continuity is good, clean the fiber according to site practice. If no site practice exists, complete
the procedure in the “Maintain the Node” chapter in the Cisco ONS 15310-CL and
Cisco ONS 15310-MA Procedure Guide.
Step3 If the alarm does not clear, see the “1.1 Network Troubleshooting Tests” section on page 1-2 to isolate
the fault causing the LOF alarm.
Step4 If the alarm does not clear, or if you need assistance conducting network troubleshooting tests, call
Cisco TAC to report a Service-Affecting(SA) problem (1-800-553-2447).
2.7.135 LOF (OCN)
Default Severity: Critical(CR), Service-Affecting (SA)
SONET Logical Objects: OCN, STSTRM
The LOF alarm occurs when a port on the reporting port has an LOF condition. The alarm indicates that
the receiving ONS 15310-CL or ONS 15310-MA has lost frame delineation in the incoming data. LOF
occurs when the SONET overhead loses a valid framing pattern for 3 ms. Receiving two consecutive
valid A1/A2 framing patterns clears the alarm.
When the alarm is raised on an OC-3 or OC-12 port, it is sometimes an indication that the OC-3 or OC-12
port expects a specific line rate and the input line rate source does not match the input line rate of the
optical receiver.

Clear the LOF (OCN) Alarm

Step1 Complete the “Clear the LOF (EC1) Alarm” procedure on page2-88.
Step2 If the alarm does not clear, or if you need assistance conducting network troubleshooting tests, call
Cisco TAC to report a Service-Affecting(SA) problem (1-800-553-2447).
2.7.136 LOF (STSTRM)
Default Severity: Critical(CR), Service-Affecting (SA)