Cisco ONS 15454 - 1.1 Troubleshooting Circuit Paths with Loopbacks

1-2
Cisco ONS 15454 Troubleshooting Guide, R8.5
November 2009
Chapter 1 General Troubleshooting
1.1 Troubleshooting Circuit Paths with Loopbacks
The remaining sections describe symptoms, problems, and solutions that are categorized according to
the following topics:
• 1.7 Using CTC Diagnostics, page 1-107—Explains how to perform card LED tests, download a
diagnostic file for Cisco Technical Support, and create a bidirectional diagnostic VT circuit.
• 1.8 Restoring the Database and Default Settings, page 1-114—Provides procedures for restoring
software data and restoring the node to the default setup.
• 1.9 PC Connectivity Troubleshooting, page 1-115—Provides troubleshooting procedures for PC
and network connectivity to the ONS 15454.
• 1.10 CTC Operation Troubleshooting, page 1-120—Provides troubleshooting procedures for
Cisco Transport Controller (CTC) login or operation problems.
• 1.11 Circuits and Timing, page 1-134—Provides troubleshooting procedures for circuit creation
and error reporting as well as timing reference errors and alarms.
• 1.12 Fiber and Cabling, page 1-139—Provides troubleshooting procedures for fiber and cabling
connectivity errors.
• 1.13 Power Supply Problems, page 1-148—Provides troubleshooting procedures for power supply
problems.
1.1 Troubleshooting Circuit Paths with Loopbacks
Use loopbacks and hairpin circuits to test newly created SONET circuits before running live traffic or to
logically locate the source of a network failure. All ONS 15454 electrical cards, OC-N cards, G-Series
Ethernet cards, and FC_MR-4 cards allow loopbacks and hairpin test circuits. Other cards do not allow
loopbacks, including E-Series Ethernet, ML-Series Ethernet, and DWDM cards such as Optical Booster
(OPT-BST), Optical Preamplifier (OPT-PRE), Optical Service Channel and Combiner/Splitter Module
(OSC-CSM), Band Optical Add/Drop Multiplexing (AD-xB-xx.x), and Channel Optical Add/Drop
Multiplexing (AD-xC-xx.x) cards. For transponder (TXP) or muxponder (MXP) loopback information,
refer to the Cisco ONS 15454 DWDM Troubleshooting Guide.
To create a loopback on a port, the port must be in the Out-of-Service and Management, Maintenance
(OOS-MA,MT) service state. After you create the loopback, the service state becomes Out-of-Service
and Management, Loopback and Maintenance (OOS-MA,LPBK & MT).
Caution Facility or terminal loopbacks can be service-affecting. To protect traffic, apply a lockout or Force
switch to the target loopback port. Basic directions for these procedures are in Chapter 2, “Alarm
Troubleshooting.” For more information about these operations, refer to the “Maintain the Node” chapter
in the Cisco ONS 15454 Procedure Guide.
Note Do not use a physical loopback to verify circuit switching time or to determine whether a situation causes
a traffic hit. Testing in this manner can cause a hit that exceeds 60 m/sec. To test switching times, place
a test set at both physical ends of the circuit.
Caution On all OC-N cards, a facility loopback applies to the entire card and not an individual circuit. Exercise
caution when using loopbacks on an OC-N card carrying live traffic.