Loopback Description; Facility Loopbacks - Cisco ONS 15454 DWDM Manual

1.1 Loopback Description

•
•
•
•
•
•
1.1 Loopback Description
Use loopbacks and hairpin circuits to test newly created circuits before running live traffic or to logically
locate the source of a network failure. All ONS 15454 and ONS 15454 SDH TXP and MXP cards allow
loopbacks and hairpin test circuits. Other cards do not allow loopbacks, including OPT-BST, OPT-PRE,
OSC-CSM, AD-xB-xx.x, and AD-xC-xx.x cards.
To create a loopback on an ANSI or SONET 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).
To create a loopback on an SDH or ETSI port, the port must be in the Locked, maintenance
administrative state and the Locked-Enabled, loopback & maintenance administrative state.
Facility or terminal loopbacks can be service-affecting. To protect traffic, apply a lockout or Force
Caution
switch to the target loopback port. Basic directions for these procedures exist in
Troubleshooting."
in the Cisco ONS 15454 DWDM Procedure Guide.
In CTC, a facility loopback is sometimes called "facility (line)" loopback, and a terminal loopback is
Note
sometimes called a "terminal (inward)" loopback. This is done to indicate the terminating direction of
the signal: a facility loopback is sent outward toward the span, whereas a terminal loopback is redirected
inward toward its originating port.

1.1.1 Facility Loopbacks

The following sections give general information about facility loopback operations and specific
information about ONS 15454 or ONS 15454 SDH card loopback activity.
Cisco ONS 15454 DWDM Troubleshooting Guide, R7.0.1
1-2
1.8 Timing, page 1-51—Provides troubleshooting procedures for circuit creation and error
reporting as well as timing reference errors and alarms.
1.9 Fiber and Cabling, page
connectivity errors.
1.10 Power Supply Problems, page
supply problems.
1.11 Power Up Problems for Node and Cards, page
shelf and card power supply problems.
1.12 Network Level (Internode) Problems, page
problems between nodes, such as fiber cuts and optical channel network connection (OCHNC)
circuit creation failure.
1.13 Node Level (Intranode) Problems, page
variable optical attenuator (VOA) startup problems as well as internal VOA control loop problems
in the 32DMX-C and 32DMX-L cards that occur due to counter-propagating light.
For more information about these operations, refer to the "Maintain the Node" chapter
1-54—Provides troubleshooting procedures for fiber and cabling
1-58—Provides troubleshooting procedures for rack power
1-60—Provides troubleshooting procedures for
1-60—Provides troubleshooting procedures for
1-84—Provides troubleshooting procedures for
Chapter 1 General Troubleshooting
Chapter 2, "Alarm
78-17742-02