1-7
Cisco ONS 15454 DWDM Troubleshooting Guide, R7.0.1
78-17742-02
Chapter 1 General Troubleshooting
1.2 Troubleshooting MXP or TXP Circuit Paths With Loopbacks
1.2 Troubleshooting MXP or TXP Circuit Paths With Loopbacks
Facility loopbacks and terminal loopbacks 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. MXP or TXP loopback tests differ from other testing
in that loopback testing does not require circuit creation. MXP or TXP client ports are statically mapped
to the trunk ports so no signal needs to traverse the cross-connect card (in a circuit) to test the loopback.
You can use these procedures on transponder cards (TXP, TXPP) or muxponder cards (MXP, MXPP)
cards. The example in this section tests an MXP or TXP circuit on a three-node bidirectional line
switched ring (BLSR) or multiplex section-shared protection ring (MS-SPRing). Using a series of
facility loopbacks and terminal loopbacks, the example scenario traces the circuit path, tests the possible
failure points, and eliminates them. The logical progression contains six network test procedures:
Note MXP and TXP card client ports do not appear when you click the Maintenance > Loopback tab unless
they have been provisioned. Do this in the card view by clicking the Provisioning > Pluggable Port
Modules tab. For information about provisioning client ports, refer to the Cisco ONS 15454 DWDM
Procedure Guide.
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 MXP or TXP port
2. A terminal loopback on the source-node MXP or TXP port
3. A facility loopback on the intermediate-node MXP or TXP port
4. A terminal loopback on the intermediate-node MXP or TXP port
5. A facility loopback on the destination-node MXP or TXP port
6. A terminal loopback on the destination-node MXP or TXP port
Note Facility and terminal loopback tests require on-site personnel.
1.2.1 Perform a Facility Loopback on a Source-Node MXP or TXP Port
This facility loopback test is performed on the node source port in the network circuit. In the testing
situation used in this example, the source muxponder or transponder port under test is located in the
source node. Facility loopback can be performed at the trunk port or at a client port. Completing a
successful facility loopback on this port isolates the source MXP or TXP port as a possible failure point.
Figure 1-3 shows the facility loopback examples on source ONS node TXP ports (client and trunk).
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