Card Behavior; Figure 1-1 Facility/Payload Loopback Process On An Stm-N Port - Cisco ONS 15600 SDH Troubleshooting Manual

Chapter 1 General Troubleshooting
Figure 1-1
Test Set
Before performing a facility loopback on an STM-N port, be sure the ASAP card contains at least two
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data communications channel (DCC) paths to the node where the card is installed. A second DCC
provides a nonlooped path to log into the node after the loopback is applied, enabling you to remove the
facility loopback. Issuing a second DCC is not necessary if you are directly connected to the
ONS 15600 SDH containing the loopbacked ASAP card.

1.1.1.2 Card Behavior

Loopbacks either terminate or bridge the loopback signal. When a port terminates a facility loopback
signal, the signal only loops back to the originating port and is not transmitted downstream. When a port
bridges a loopback signal, the signal loops back to the originating port and is also transmitted
downstream.
The loopback itself is listed in the Conditions window. For example, the window would list the
LPBKFACILITY condition for a tested port. (The Alarms window will show AS-MT, which means that
alarms are suppressed on the facility during loopback.) In Software Release 8.0, an option in node
defaults allows you to specify that loopback conditions be reported as alarms, even though the port or
circuit is Locked,maintenance.
In addition to the Conditions window listing, the following behaviors occur:
•
•
A lockout of protection must be executed before putting a two-fiber or four-fiber MS-SP Ring span into
Caution
a facility loopback state. That is, a span lockout of one side (such as the east side) of a two-fiber MS-SP
Ring is required before operating a facility loopback on the same (east) side of the ring. A span lockout
of one protection side (such as the east protection side) of a four-fiber MS-SP Ring is required before
operating a facility loopback on the same (east) side working line of the ring. If you do not execute the
lockout prior to creating the loopback, the ring can become stuck in an anomalous state after you release
the loopback.
July 2010
Facility/Payload Loopback Process on an STM-N Port
STM-Nx SSXC
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If an electrical or optical port is in the Locked-enabled, disabled service state, it injects an alarm
indication signal (AIS) upstream and downstream.
When an electrical or optical port is placed in the Locked-enabled,maintenance service state
before loopback testing, the port clears the AIS signal upstream and downstream unless there is a
service-affecting defect that would also cause an AIS signal to be injected. For more information
about placing ports into alternate states for testing, refer to the "Change Card Settings" chapter of
the Cisco ONS 15600 SDH Procedure Guide.
STM-Ny
Cisco ONS 15600 SDH Troubleshooting Guide, R8.0
1.1.1 Facility Loopbacks
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