Cisco ONS 15454 Troubleshooting Manual page 8

1.3 Identify Points of Failure on a DS-N Circuit Path
1.3 Identify Points of Failure on a DS-N Circuit Path
Facility (line) loopbacks, terminal (inward) loopbacks, and hairpin circuits are often used to test a 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 a DS-N circuit on a two-node, bidirectional line switched ring (BLSR).
Using a series of facility loopbacks, terminal loopbacks, and hairpins, the path of the circuit is traced
and the possible points of failure are tested and eliminated. A logical progression of five network test
procedures apply to this sample scenario:
Note The test sequence for your circuits will differ according to the type of circuit and network topology.
West to east direction (left to right):
1.
2.
3.
4.
East to west direction (right to left):
1.
2.
3.
4.
All loopback tests require on-site personnel.
Note
1.3.1 Perform a Facility (Line) Loopback on a Source DS-N Port (West to East)
The facility (line) loopback test is performed on the node source port in the network circuit, in this
example, the DS-N port in the source node. Completing a successful facility (line) loopback on this port
isolates the cabling, the DS-N card, and the EIA as possible failure points.
of a facility loopback on a source DS-N port.
Figure 1-10 A Facility (Line) Loopback on a Circuit Source DS-N Port
Test Set
Cisco ONS 15454 Troubleshooting Guide, R4.6
1-8
A facility (line) loopback on the source node DS-N
A hairpin on the source node DS-N
An XC loopback on the destination node OC-N STS (carrying the DS-N circuit)
A terminal (inward) loopback on the destination node DS-N
A facility (line) loopback on the destination node DS-N
A hairpin on the destination node DS-N
An XC loopback on the source node OC-N STS (carrying the DS-N circuit)
A terminal (inward) loopback on the source node DS-N
Source
ONS Node
DS-N XC OC-N
Chapter 1 General Troubleshooting
Figure 1-10 shows an example
Destination
ONS Node
OC-N XC DS-N
November 2004