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Cisco ONS 15327 Troubleshooting Guide, R3.4
April 2003
Chapter 1 General Troubleshooting
Identify Points of Failure on a DS-N Circuit Path
1.2.5 Perform a Facility Loopback on a Destination XTC Card
The facility loopback test is performed on the last port in the circuit, in this case the XTC port in the
destination node. Completing a successful facility loopback on this port isolates the possibility that the
destination node cabling, MIC card, or line interface is responsible for a faulty circuit. Figure 1-11
shows an example of a facility loopback on a destination node XTC port.
Figure 1-11 Facility Loopback on a Destination XTC Card
Caution Performing a loopback on an in-service circuit is allowed but is service-affecting.
Note Loopbacks operate only on ports in the OOS_MT state.
Procedure: Create a Facility Loopback Circuit on a Destination XTC Port
Step 1 Connect an electrical test set to the port you are testing:
a. If you just completed the “Perform a Hairpin on a Destination Node XTC Port” procedure on
page 1-14, leave the electrical test set hooked up to the DS-N port in the destination node.
b. If you are starting the current procedure without the electrical test set hooked up to the DS-N port,
use appropriate cabling to attach the Tx and Rx terminals of the electrical test set to the DSx panel
or the EIA connectors for the port you are testing. Both Tx and Rx connect to the same port.
c. Adjust the test set accordingly.
Step 2 Use CTC to create the facility loopback on the port being tested:
a. In node view, double-click the card where you are performing the loopback.
b. Click the Maintenance > Loopback tabs.
c. Select Facility (Line) from the Loopback Type column for the port being tested. If this is a multiport
card, select the row appropriate for the desired port.
d. Click the Apply button.
e. Click the Yes button in the Confirmation Dialog box.
Note It is normal for a LPBKFACILITY condition to appear during loopback setup. The condition
clears when you remove the loopback.
MIC OC-N OC-N
DS-N
DS-N
Facility loopback
Test Set A
XTC
XTC
ONS 15327
Source
ONS 15327
Destination
76192
MIC