Testing Interfaces

Testing interfaces allows you to troubleshoot problems and to check the quality of links at various layers in the interface stack. The router supports the following test options:

• Transmission of BERT patterns to remote devices
• Local loopback—Loops the data back toward the router; on supported line modules, also sends an alarm indication signal (AIS) out toward the network
• Network loopback—Loops the data toward the network before the data reaches the frame
• Payload loopback—Loops the data toward the network after the framer processes the data
• Remote loopback—Provides the ability to:
  • Request that remote devices enter into loopback
  • Be placed in loopback by remote devices

Sending BERT Patterns

The router can send BERT patterns from different layers in the interface stack on frame-based T3 interfaces.

For a list of the modules that support bit error rate tests, see ERX Module Guide, Appendix A, Module Protocol Support.

To send BERT patterns:

1. Select a controller.
   host1(config)#controller t3 3/2
2. Configure a specific layer in the interface to generate BERT patterns.
   host1(config-controll)#bert pattern 2^11 interval 10

   For information about BERT patterns, see References.

Enabling Local, Network, and Payload Loopback

To enable local, network, or payload loopback testing of a T3 or E3 line, use the clock source and loopback commands from Controller Configuration mode.

1. Change the clock source to internal.
   host1(config-controll)#clock source internal module
2. Specify a loopback.
   host1(config-controll)#loopback local

Enabling Remote Loopback

You can enable remote loopback capability on frame-based T3 interfaces configured to use C-bit framing. Remote loopback is not supported on E3 ATM, E3 FRAME, and T3 ATM interfaces.

For a list of the modules that support remote loopback, see ERX Module Guide, Appendix A, Module Protocol Support.

To enable remote loopback:

1. Change the clock source to internal.
   host1(config-controll)#clock source internal module
2. Ensure that the line is configured to use C-bit framing, which is the default for frame-based T3 interfaces.
   host1(config-controll)#framing c-bit
3. Configure one of the following loopback tests:
   • Set the loopback to remote to request that a remote device connected on a T3 interface enter into a loopback.
     host1(config-controll)#loopback remote
   • Configure the T3 interface to enable or disable the ability to enter into a loopback initiated by a remote device, as follows:
     • Issue the equipment customer loopback command to enable the router to enter into loopback when it receives an appropriate signal from the remote device.
       host1(config-controll)#equipment customer loopback
     • Issue the equipment network loopback command to disable the ability to enter into loopback initiated by a remote device.
       host1(config-controll)#equipment network loopback