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Cisco ONS 15327 Troubleshooting Guide, R3.4
April 2003
Chapter1 General Troubleshoo ting Identify Points of Failure on a DS-N Circuit Path
1.2.1 Perform a Facility Loopback on a Source XTC Port
The facility loopback test is performed on the node source port in the network circuit; in this example,
the test is routed through the MIC card and performed on the XTC port in the source node. Completing
a successful facility loopback on this port isolates the cabling, MIC card, and XTC card as possible
failure points. Figure 1-7 shows an example of a facility loopback on a source node XTC port.
Figure1-7 Facility Loopback on a Source XTC Port
Caution Performing a loopback on an in-service circuit is service-affecting.
Note Loopbacks operate only on ports in the out of service-maintenance (OOS_MT) st ate.

Procedure: Create the Facility Loopback on the Source XTC Port

Step 1 Connect an electrical test set to the port you are testing.
Use appropriate cabling to attach the transmit (Tx) and receive (Rx) terminals of the e lectrical t est set to
the MIC card, which interfaces with the XTC card. Both Tx and Rx connect to the same port. 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. Choose OOS_MT from the State column for the port being tested. If this is a multiport card, select
the appropriate row for the port being tested.
d. Choose Facility (Line) from the Loopback Type column for the port being tested. If this is a
multiport card, select the appropriate row for the port being tested.
e. Click the Apply button.
f. 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.
XTC XTC
MIC OC-N
ONS 15327
Source
OC-N MIC
ONS 15327
Destination
DS-N
DS-N
Facility loopback
Test Set A
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