Specifications

8-4
Cisco MGX 8260 Command Line Interface Guide
Release 1.2, Part Number 78-10987-01 Rev. B0, January, 2002
Chapter 8 Troubleshooting
Performing BERT Tests
SONET Loopback
To perform a SONET loopback test, follow these steps:
Step 1 Activate the loopback using the chsonetln command, specifying the slot, line, and loopback type. Refer
to the following table for the loopback type:
Note Serial and parallel loops are both local loopback states.
For example, the following command loops line 2 on slot 9:
chsonetln 9.2 # # # 2
The system activates the loopback and changes the corresponding line LED to blinking yellow.
Step 2 Perform SONET signal tests, as appropriate.
Step 3 Release the loopback by reentering the chds3ln command, but specify the dsx3NoLoop parameter. For
example, to release the loopback on slot 7, line 2, enter the command as follows:
chsonetln 7.2 # # # # 1
The system releases the loopback, changes the line LED to green, and returns the line to normal
operation.
Step 4 Verify that the loopback is clear using the lssonetln command.
Performing BERT Tests
Bit Error Rate Tests (BERT) check the error performance of DS1/E1 lines. Often used in conjunction
with loopback tests, this test helps isolate equipment or line segments with degraded performance.
Typically, you activate loopback on one end of the communications link and activate the BERT test on
the other. Do not activate loopback and BERT together on the same equipment.
Warning BERT tests interrupt service. Perform in a pre-arranged maintenance window or when
the line is down.
Value Name
1 No loop
2Line loop
3 Serial loop
4 Parallel loop