Cisco ONS 15454 DWDM Manual page 5

Chapter 1 General Troubleshooting
1.1.2.1 General Behavior
A terminal loopback tests a circuit path as it passes through a TXP or MXP card and loops back. For
example, as shown in
The first is a terminal loopback at the client port. In this situation, the test set traffic comes in through
the TXP trunk port, travels through the card, and turns around because of the terminal loopback in effect
on the card just before it reaches the LIU of the client port. The signal is then sent back through the card
to the trunk port and back to the test set.
The second is a terminal loopback at the trunk port. In this situation, the test set traffic comes in through
the TXP client port, travels through the card, and turns around because of the terminal loopback in effect
on the card just before it reaches the LIU of the trunk port. The signal is then sent back through the card
to the client port and back to the test set.
This test verifies that the terminal circuit paths are valid, but does not test the LIU on the TXP card.
Figure 1-2
Test Set
Test Set
1.1.2.2 Card Behavior
ONS 15454 and ONS 15454 SDH terminal port loopbacks can either terminate or bridge the signal. TXP
terminal loopbacks are terminated as shown in
a terminal 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. Client card terminal loopback bridging and terminating behaviors are
listed in
78-17742-02
Figure 1-2, there are two types of terminal loopbacks shown for a TXP card.
Terminal Loopback on a TXP Card
Terminal loopback at client port
Client port
TXP
Trunk port
Terminal loopback at trunk port
Client port
TXP
Trunk port
Table 1-2.
Table 1-2. During terminal loopbacks, if a port terminates
Cisco ONS 15454 DWDM Troubleshooting Guide, R7.0.1
1.1.2 Terminal Loopbacks
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