Terminal Loopbacks - Cisco NCS 2000 series Troubleshooting Manual

General Troubleshooting
Locked-enabled,maintenance & loopback service state and the remaining client and trunk ports can be in any
other service state.
When you apply a facility loopback on the GE_XP, 10GE_XP, GE_XPE, and 10GE_XPE cards, the ifInDiscard
counters increment continuously.

Terminal Loopbacks

The following sections give general information about terminal loopback operations and specific information
about card loopback activity.
General Behavior
A terminal loopback tests a circuit path as it passes through a TXP, MXP, or ADM-10G card and loops back.
For example, as shown in
terminal loopbacks shown for a TXP card.
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 2: Terminal Loopback on a TXP Card
Figure 2: Terminal Loopback on a TXP Card, on page
Cisco NCS 2000 series Troubleshooting Guide, Release 11.0
Terminal Loopbacks
5, there are two types of
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