Troubleshooting guide

8-16
Cisco Broadband Local Integrated Services Solution Troubleshooting Guide
OL-5169-01
Chapter 8 Troubleshooting the Cisco Catalyst 6509
Troubleshooting Serial Lines
Terminating a BER test
To terminate a BER test, type
no t1 t1-line-number bert
where t1-line-number is 1–28.
Example:
• Terminate the BER test running on T1 line 10 on the CT3 line card.
Router(config)# controller T3 1/0/0
Router(config-controller)# no t1 10 bert
Using Loopback Tests
The following sections describe the configuration and use of loopback tests in problem isolation:
• Configuring the Loopback Mode for a T3 Controller, page 8-16
• Configuring a T3 Controller to Respond to Remote Loopback Commands, page 8-17
• Configuring the Loopback Mode for a Gigabit Ethernet Interface, page 8-17
• Configuring the Loopback Mode for an OC-12 POS Interface, page 8-17
Configuring the Loopback Mode for a T3 Controller
You can configure the loopback modes for a T3 controller by using the loopback command:
loopback [local | network | remote]
The default loopback mode for the T3 controller is no loopback.
To return the T3 controller to its default condition, use the no form of the command.
Examples:
• Configure a T3 controller for local loopback:
Router(config)# controller T3 1/0/0
Router(config-controller)# loopback local
Local loopback simultaneously loops all channels toward the router and transmits a T3 AIS to the
network. You can use local loopback to diagnose problems with the port when isolated from the
network cables.
• Configure a T3 port for network loopback:
Router(config)# controller T3 1/0/0
Router(config-controller)# loopback network
Network loopback loops the T3 line back towards the network and can be used to diagnose problems
with cables from the central switching office to the port.
• Configure a T3 port for remote loopback:
Router(config)# controller T3 1/0/0
Router(config-controller)# loopback remote
Remote loopback sends a command to loop the T3 line at the far end (central office). It can be used
to diagnose problems with cables from the port adapter to the switching office.