Specifications

8-2
Cisco MGX 8260 Command Line Interface Guide
Release 1.2, Part Number 78-10987-01 Rev. B0, January, 2002
Chapter 8 Troubleshooting
Performing Loopback Tests
Warning Loopback testing interrupts service. Perform during in a pre-arranged maintenance
window or when the line is down.
DS1/E1 Loopback
To perform a DS1/E1 loopback test, follow these steps:
Step 1 Activate the loopback using the chds1ln. Specify the first and last parameters—the slot and line
number, delimited by a period, of the DS1 line and the type of loopback test. Refer to the following
table for loopback types:
For example, the following command loops line 2 on slot 3:
chds1ln 3.2 # # # # 2
The system activates the loopback and changes the corresponding line LED to blinking yellow.
Step 2 Perform DS1/E1 signal tests, such as the BERT test. For more information, see the “Performing BERT
Tests” section on page 8-4.
Step 3 Release the loopback by entering the chds1ln command again, but specify the dsx1NoLoop parameter.
For example, to release the loopback on slot 3, line 2, enter the command as follows:
chds1ln 3.2 # # # # 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 lsds1ln command.
Value Name
1 dsx1NoLoop
2 dsx1PayloadLoop
3dsx1LineLoop
4 dsx1OtherLoop (local)