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Cisco ONS 15327 Troubleshooting Guide, R3.4
April 2003
Chapter 1 General Troubleshooting
Identify Points of Failure on an OC-N Circuit Path
• Choose the appropriate state (IS, OOS, or OOS_AINS) from the State column for the port being
tested.
• Click the Apply button.
• Click the Yes button in the Confirmation Dialog box.
d. The entire DS-N circuit path has now passed its comprehensive series of loopback tests. This circuit
qualifies to carry live traffic.
Step 4 If the test set indicates a faulty circuit, contact the Cisco TAC.
1.3 Identify Points of Failure on an OC-N Circuit Path
Facility loopbacks, terminal loopbacks, and cross-connect loopback circuits are often used together to
test the circuit path through the network or to logically isolate a fault. Performing a loopback test at each
point along the circuit path systematically isolates possible points of failure.
The example in this section tests an OC-N circuit on a three-node BLSR. Using a series of facility
loopbacks and terminal loopbacks, the path of the circuit is traced and the possible points of failure are
tested and eliminated. A logical progression of seven network test procedures applies to this sample
scenario:
1. Facility loopback on the source-node OC-N port
2. Cross-connect loopback on the source-node OC-N port
3. Terminal loopback on the source-node OC-N port
4. Facility loopback on the intermediate-node OC-N port
5. Terminal loopback on the intermediate-node OC-N port
6. Facility loopback on the destination-node OC-N port
7. Terminal loopback on the destination-node OC-N port
Note The test sequence for your circuits differs according to the type of circuit and network topology.
Note All loopback tests require on-site personnel.
1.3.1 Perform a Facility Loopback on a Source-Node OC-N Port
The facility loopback test is performed on the node source port in the network circuit, in this example,
the source OC-N port in the source node. Completing a successful facility loopback on this port isolates
the OC-N port as a possible failure point. Figure 1-12 on page 1-22 shows an example of a facility
loopback on a circuit source OC-N port.