Network Troubleshooting Tests; Facility Loopbacks; General Behavior; Chapter 1 General Troubleshooting - Cisco ONS 15600 SDH Troubleshooting Manual

1.1 Network Troubleshooting Tests

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1.1 Network Troubleshooting Tests
Use loopbacks to test newly created circuits before running live traffic or to logically locate the source
of a network failure. All ONS 15600 SDH optical (STM-N) cards allow loopbacks.
Caution On optical cards, a loopback can be applied only if the port state is Locked,maintenance for facility,
terminal, and payload loopbacks, and the circuit state is Locked,maintenance for cross-connect
loopbacks.
Do not use loopbacks to verify circuit switch times or traffic hits because it could exceed 60 msec. For
Note
switch times, a test set should be placed at both ends of the circuits.
When an entity is put in the administrative state, the ONS 15600 SDH suppresses all standing alarms
Note
on that entity. All alarms and events appear on the Conditions tab. You can change this behavior for the
LPBKFACILITY, LPBKPAYLD, and LPBKTERMINAL alarms. To display these alarms on the Alarms
tab, set the NODE.general.ReportLoopbackConditionsOnPortsInLocked,maintenance to TRUE on the
NE Defaults tab.

1.1.1 Facility Loopbacks

The following sections give general information about facility loopback operations and specific
information about ONS 15600 SDH card loopback activity.

1.1.1.1 General Behavior

A facility loopback tests the line interface unit (LIU) of an ASAP card or STM-16 card and related
cabling. After applying a facility loopback on a port, use a test set to run traffic over the loopback. A
successful facility loopback isolates the LIU or the cabling plant as the potential cause of a network
problem. To test an STM-N port or Ethernet port, connect an optical test set to the port and perform a
facility loopback. Alternately, use a loopback or hairpin circuit on a card that is farther along the circuit
path.
CTC sometimes calls a facility loopback a facility (line) loopback. This is done to clarify the direction
Note
that the loopback signal travels, that is, out from the facility toward the span.
Figure 1-1
Cisco ONS 15600 SDH Troubleshooting Guide, R8.0
1-2
1.10 Power Supply Problems, page
power supply issues.
shows a facility/payload loopback on an STM-N port.
1-74—Provides troubleshooting information for common

Chapter 1 General Troubleshooting

July 2010