Figure - Cisco ONS 15454 Troubleshooting Manual

Chapter 1 General Troubleshooting
Bridged DS-N and OC-N terminal loopback examples are shown in

Figure 1-7

Terminal Loopback on a DS-N Card with a Bridged Signal
DS-N
Test Set
Figure 1-8 Terminal Loopback on an OC-N Card with a Bridged Signal
OC-N
Test Set
G-Series Ethernet cards placed in terminal loopback have different performance monitoring behaviors
from other ONS 15454 cards. (For more information about performance monitoring counters, see the
"Performance Monitoring" chapter in the Cisco ONS 15454 Reference Manual.) Setting a terminal
loopback on the G-Series Ethernet card might not stop the Tx Packets counter or the Rx Packet counters
on the CTC card-level view Performance > Statistics page from increasing. The counters can increment
even though the loopbacked port has temporarily disabled the transmit laser and is dropping any received
packets.
The Tx Packet statistic continues to increment because the statistics are not based on packets transmitted
by the transmit (Tx) laser but on the Tx signal inside the G-Series card. In normal in-service port
operation, the Tx signal being recorded results in the Tx laser transmitting packets, but in a terminal
loopback this signal is being looped back within the G-Series card and does not result in the Tx laser
transmitting packets.
The Rx Packet counter might also continue to increment when the G-Series card is in terminal loopback.
Receive (Rx) packets from any connected device are dropped and not recorded, but the internally
loopbacked packets follow the G-Series card's normal receive path and register on the Rx Packet counter.
The loopback itself is listed in the Conditions window. For example, the Conditions window would list
the LPBKTERMINAL condition or the LPBKFACILITY condition for a tested port. (The Alarms
window would show AS-MT, which indicates that all alarms are suppressed on the port during loopback
testing.)
The following behaviors also occur during loopback:
•
November 2009
Source
ONS Node
XC OC-N
Source
ONS Node
XC OC-N
If an electrical or optical port is in the OOS-MA,DSBLD service state, the port injects an AIS signal
upstream and downstream.
Destination
ONS Node
OC-N XC DS-N
Destination
ONS Node
OC-N XC OC-N
Cisco ONS 15454 Troubleshooting Guide, R8.5
1.1.2 Terminal Loopbacks
Figure 1-7 and Figure 1-8.
Test Set
Test Set
1-7