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Chapter 1
General Troubleshooting
1.1.2 Terminal Loopbacks
The following sections give general information about terminal loopback operations and specific
information about ONS 15454 SDH card loopback activity.
1.1.2.1 General Behavior
A terminal loopback tests a circuit path as it passes through the XC-VXL cross-connect card loops back
from the card with the loopback.
traffic comes into the electrical card and goes through the cross-connect card to the STM-N card. The
terminal loopback on the STM-N card turns the signal around before it reaches the LIU and sends it back
through the cross-connect card to the E1-N-14 card. This test verifies that the cross-connect card and
terminal circuit paths are valid, but does not test the LIU on the STM-N card.
Figure 1-4
Test Set
In CTC, STM-N cards with terminal loopbacks show an icon
on other cards in this release.
Figure 1-5
Figure 1-6
STM-N card and goes through the cross-connect card to the E1-N-14 card. The terminal loopback on the
E1-N-14 card turns the signal around before it reaches the LIU and sends it back through the
cross-connect card to the STM-N card. This test verifies that the cross-connect card and terminal circuit
paths are valid, but does not test the LIU on the E1-N-14 card.
Figure 1-6
E3-12
July 2005
Figure 1-4
Terminal Loopback Path on an STM-N Card
E3-12
XC
Terminal Loopback Indicator
shows a terminal loopback on an E1-N-14 electrical card. The test-set traffic comes in on the
Terminal Loopback Process on an E1-N-14 Card
XC
STM-N
shows a terminal loopback on an STM-N card. The test-set
STM-N
(Figure
Test Set
Cisco ONS 15454 SDH Troubleshooting Guide, R5.0
1.1.2 Terminal Loopbacks
1-5). Loopback icons are not shown
1-5
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