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1.1.2 Terminal Loopbacks
1.1.2.2 ONS 15454 SDH Card Behavior
ONS 15454 SDH port loopbacks can either terminate or bridge the loopback signal. In the
ONS 15454 SDH system, all optical, electrical, Ethernet, MXP, TXP, and FC_MR facility loopbacks are
terminated as shown in
loopback signal while others terminate it.
If a port terminates a terminal or facility loopback signal, the signal only loops back to the originating
port and is not transmitted downstream. If the port bridges a loopback signal, the signal loops back to
the originating port and is also transmitted downstream.
ONS 15454 SDH card terminal loopback bridging and terminating behaviors are listed in
Note
In
Table
AIS is injected downstream for all cards except Ethernet cards.
Table 1-2
Card/Port
DS3i-N-12
E1-N
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 Ethernet terminal loopback is terminated and Ethernet transmission is
2. For the STM1-E card, only Ports 9 through 12 can be placed in E4 mode.
Bridged E1-N-14 and STM-N terminal loopback examples are shown in
Figure 1-7
Terminal Loopback on an E1-N-14 Card with Bridged Signal
E1N
Test Set
Cisco ONS 15454 SDH Troubleshooting Guide, R5.0
1-6
Table
1-2, no AIS signal is injected if the signal is bridged. If the signal is terminated, an applicable
ONS 15454 SDH Card Terminal Loopback Behavior
disabled. No AIS is inserted for Ethernet, but a TPTFAIL alarm is raised on the
far-end Ethernet port.
Source
ONS Node
XC
STM-N
1-2. During terminal loopbacks, some ONS 15454 SDH cards bridge the
Terminal Loopback Signal
Bridged
Terminated
1
Terminated
Bridged
Terminated
Bridged
Terminated
Terminated
2
Bridged
Destination
ONS Node
STM-N
XC
E1N
Chapter 1
General Troubleshooting
Table
1-2.
Figure 1-7
and
Figure
1-8.
Test Set
July 2005
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