Card Behavior - Cisco NCS 2000 series Troubleshooting Manual

General Troubleshooting
Figure 1: Facility Loopback Path on a Near-End Transponder Card
Caution
Before performing a facility loopback on a TXP card, be sure that the card contains at least two data
communications channel (DCC) paths to the node where the card is installed. A second DCC provides a
nonlooped path to log into the node after the loopback is applied, enabling you to remove the facility loopback.
Ensuring a second DCC is not necessary if you are directly connected to the node containing the loopback
card.
Caution Ensure that the facility being loopbacked is not being used by the node for line timing. If it is, a timing loop
will be created.

Card Behavior

Port loopbacks either terminate or bridge the loopback signal. All MXP and TXP facility loopbacks are
terminated as shown in the following 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.
Note
In the following table, no alarm indication signal (AIS) is injected if the signal is bridged. If the signal is
terminated, an applicable AIS is injected downstream.
Cisco NCS 2000 series Troubleshooting Guide, Release 11.0
Card Behavior
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