Cisco ONS 15454 - 1.4 Troubleshooting Optical Circuit Paths With Loopbacks

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Cisco ONS 15454 Troubleshooting Guide, R8.5
November 2009
Chapter 1 General Troubleshooting
1.3.2 DS-3E and DS3i-N-12 Inhibit Loopback
1.3.2 DS-3E and DS3i-N-12 Inhibit Loopback
DS-3E and DS-3i-N-12 cards respond to (but do not send) DS-3-level FEAC codes. You can inhibit
FEAC response on ports for these cards using the Inhibit Lbk check box on their Maintenance windows.
1.3.3 DS3XM-6 and DS3XM-12 Inhibit FEAC Loopback
DS3XM-6 and DS3XM-12 ports and transmuxed DS-1 circuits initiate loopbacks when they receive
FEAC line loop codes. If the Inhibit FE Lbk check box is checked for a DS-3 port, that port ignores any
FEAC line loop codes it receives and will not loop back (return them). Only DS-3 ports can be
configured to inhibit FEAC loopback responses; individual DS-1 ports (accessed on the DS3XM DS1
tab) cannot inhibit their responses. If you inhibit a DS-3 port’s far end loopback response, this DS-3 port
and the DS-1 lines it contains are not restricted from terminal or facility loopbacks.
1.3.4 FEAC Alarms
When an ONS 15454 port receives an activation code for a FEAC loopback, it raises the
“LPBKDS3FEAC” condition on page 2-168. The condition clears when the port receives the command
to deactivate the FEAC loopback. If a node sends a FEAC loopback command to the far end, the sending
node raises a “LPBKDS3FEAC-CMD” condition on page 2-168 for the near-end port.
1.4 Troubleshooting Optical Circuit Paths With Loopbacks
Facility loopbacks, terminal loopbacks, and cross-connect loopback circuits are often used together to
test the circuit path through the network or to logically isolate a fault. Performing a loopback test at each
point along the circuit path systematically isolates possible points of failure.
The procedures in this section apply to OC-N cards. For instructions on G-Series Ethernet cards, see the
“1.5 Troubleshooting Ethernet Circuit Paths With Loopbacks” section on page 1-68. The example in
this section tests an OC-N circuit on a three-node BLSR. Using a series of facility, cross-connect, and
terminal loopbacks, the example scenario traces the circuit path, tests the possible failure points, and
eliminates them. The logical progression contains seven network test procedures:
Note The test sequence for your circuits will differ according to the type of circuit and network topology.
1. A facility loopback on the source-node OC-N port
2. A terminal loopback on the source-node OC-N port
3. A cross-connect loopback on the source OC-N port
4. A facility loopback on the intermediate-node OC-N port
5. A terminal loopback on the intermediate-node OC-N port
6. A facility loopback on the destination-node OC-N port
7. A terminal loopback on the destination-node OC-N port
Note Facility and terminal loopback tests require on-site personnel.