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1.1.1 Facility Loopbacks
1.1.1.2 ONS 15454 SDH Card Behavior
ONS 15454 SDH port loopbacks either terminate or bridge the loopback signal. All ONS 15454 SDH
optical, electrical, Ethernet, MXP, TXP, and FC_MR facility loopbacks are terminated as shown in
Table
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.
In
Table
Note
terminated, an AIS is injected downstream for all cards except Ethernet cards.
Table 1-1
Card/Port
DS3i-N-12
E1-N-14
G-Series Ethernet
MXP, MXPP trunk ports
MXP, MXPP client ports
TXP, TXPP trunk ports
TXP, TXPP client ports
STM1-E in STM1-E mode
STM1-E ports 9-12 in E4 mode
1. G-Series facility loopback is terminated and no AIS is sent downstream. However,
2. For the STM1-E card, only Ports 9 through 12 can be placed in E4 mode.
The loopback itself is listed in the Conditions window. For example, the window would list the
LPBKTERMINAL condition or 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 addition to the Conditions window listing, the following behaviors occur:
•
•
MXP and TXP card facility loopbacks behave differently from other ONS 15454 SDH cards. With a
client-side MXP or TXP facility loopback, the client port is in the Locked-enabled,maintenance &
loopback service state, however the remaining client and trunk ports can be in any other service state.
For MXP and TXP cards in a trunk-side facility loopback, the trunk port is in the
Locked-enabled,maintenance & loopback service state and the remaining client and trunk ports can be
in any other service state.
Cisco ONS 15454 SDH Troubleshooting Guide, R5.0
1-4
1-1.
1-1, no alarm indication signal (AIS) signal is injected if the signal is bridged. If the signal is
ONS 15454 SDH Card Facility Loopback Behavior
the Cisco Link Integrity signal continues to be sent downstream.
If an electrical or optical port is in the Locked-enabled,disabled service state, it injects an AIS signal
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 Cisco ONS 15454 SDH Procedure
Guide Chapter 5, "Turn Up Network."
Facility Loopback Signal
Terminated
Terminated
1
Terminated
Bridged
Terminated
Bridged
Terminated
Terminated
2
Terminated
Chapter 1
General Troubleshooting
July 2005
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