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Chapter 1
General Troubleshooting
Figure 1-10
External signals from
and to other equipment
When creating cross-connect loopbacks, consult the following rules:
•
•
1.2 Troubleshooting Electrical Circuit Paths With Loopbacks
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. These procedures apply to DS-3 and
E-1 electrical cards.
The example in this section tests an electrical circuit on a two-node multiplex section-shared protection
ring (MS-SPRing). Using a series of facility loopbacks, terminal loopbacks, hairpins, and where
appropriate cross-connect loopbacks (on optical paths carrying electrical circuits), 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 applies 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.
July 2005
NE with SDH Cross-Connect Loopback Function
OOS
You can create a cross-connect loopback on all working or protect optical ports unless the protect
port is used in a 1+1 protection group and is in working mode.
If a terminal or facility loopback exists on a port, you cannot use the cross-connect loopback.
A facility (line) loopback on the source-node electrical card (DS-3 or E-1)
A hairpin on the source-node electrical port
An XC loopback on the destination-node STM-N virtual concatenation (VC, carrying the electrical
circuit)
A terminal (inward) loopback on the destination-node electrical port
A facility (line) loopback on the destination-node electrical port
A hairpin on the destination-node electrical port
An XC loopback on the source-node STM-N VC (carrying the electrical circuit)
A terminal (inward) loopback on the source-node electrical port
1.2 Troubleshooting Electrical Circuit Paths With Loopbacks
Equipment to perform
framing, scrambling, etc.
(such as signal terminating equipment)
O/E
R
E/O
T
Cisco ONS 15454 SDH Troubleshooting Guide, R5.0
AIS
Internal signals to and from
other equipment in the NE
1-9
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