Network Troubleshooting Tests - Cisco ONS 15454 Troubleshooting Manual

1.1 Network Troubleshooting Tests

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1.1 Network Troubleshooting Tests
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 OC-N cards, transponder cards (TXP,
TXPP), muxponder (MXP) cards, and G-Series Ethernet cards allow loopbacks and hairpin test circuits.
Other cards do not allow loopbacks. These include ONS E-Series Ethernet, ML-Series Ethernet, and
DWDM cards such as OPT-BST, OPT-PRE, OSC-CSM, band add-drop cards, and channel add-drop
cards.
Facility (line) or terminal loopbacks can be service-affecting. To protect traffic, apply a lockout or Force
Caution
switch to the target loopback port. For more information about these operations, refer to the
Cisco ONS 15454 Procedure Guide.
On OC-N cards, a facility (line) loopback applies to the entire card and not an individual circuit. Exercise
Caution
caution when using loopbacks on an OC-N card carrying live traffic.
A facility (line) loopback tests the line interface unit (LIU) of a card, the EIA (electrical interface
assembly), 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, the EIA, or the cabling plant as the
potential cause of a network problem.
Figure 1-1
Test Set
To test the LIU on an OC-N card, connect an optical test set to the OC-N port and perform a facility (line)
loopback or use a loopback or hairpin circuit on a card that is farther along the circuit path.
shows a facility loopback on an OC-N card.
Cisco ONS 15454 Troubleshooting Guide, R4.6
1-2
Fiber and Cabling—Provides troubleshooting procedures for fiber and cabling connectivity errors.
Power and LED Tests—Provides troubleshooting procedures for power supply and LED indicator
problems.
Facility (Line) Loopback Process on a DS-N Card
DS-N
Figure 1-1 shows a facility loopback on a DS-N card.
XC OC-N
Chapter 1 General Troubleshooting
Figure 1-2
November 2004