Cisco ONS 15454 SDH Specifications Page 82

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Cisco ONS 15454 SDH Troubleshooting and Maintenance Guide, R3.3
May 2002
Chapter 2 General Troubleshooting
Network Troubleshooting Tests
Figure 2-1 The facility loopback process on an E3-12 card
Figure 2-2 shows a facility loopback on a STM-N card.
Caution Before performing a facility loopback on an STM-N card, make sure the card contains at least two
SDCC paths to the node where the card is installed. A second SDCC path provides a non-looped path
to log into the node after the loopback is applied, thus enabling you to remove the facility loopback.
Ensuring a second SDCC is not necessary if you are directly connected to the ONS 15454 SDH
containing the loopback OC-N.
Figure 2-2 The facility loopback process on a STM-N card
A terminal loopback tests a circuit path as it passes through the cross-connect card (XC10G) and as it
loops back from the card being tested. Figure 2-3 shows a terminal loopback on an STM-N card. The
test-set traffic comes in on the E3-12 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 through the cross-connect card to the E3-12 card. This test verifies that the cross-connect card and
circuit paths are valid, but does not test the LIU on the STM-N card.
Figure 2-3 The terminal loopback process on an STM-N card
To test the LIU on an STM-N card, connect an optical test set to the STM-N card ports and perform a
facility loopback or use a loopback or hairpin on a card that is farther along the circuit path. Figure 2-4
shows a terminal loopback on an E3-12 card. The test-set traffic comes in on the STM-N card and goes
through the cross-connect card to the E3-12 card. The terminal loopback on the E3-12 card turns the
76170
E3-12 STM-NXC
Test Set
E3-12 STM-NXC
Test Set
78261
76177
STM-N
Test Set
XCE3-12
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