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.

bert

• Use to enable bit error rate tests using the specified pattern on a T3 interface.
• Unlike other configuration commands, bert is not stored in NVRAM.
• Specify one of the following test patterns:
  • 0s—Repetitive test pattern of all zeros, 00000...
  • 1s—Repetitive test pattern of all ones, 11111...
  • 2^9—Pseudorandom test pattern, 511 bits in length
  • 2^11—Pseudorandom test pattern, 2047 bits in length
  • 2^15—Pseudorandom test pattern, 32,767 bits in length
  • 2^20—Pseudorandom test pattern, 1,048,575 bits in length
  • 2^20-QRSS—Pseudorandom QRSS test pattern, 1,048,575 bits in length
  • 2^23—Pseudorandom test pattern, 8,388,607 bits in length
  • alt-0-1—Repetitive alternating test pattern of zeros and ones, 01010101...
• Specify the duration of the test in the range 1–1440 minutes.
• Example

  host1(config-controll)#bert pattern 2^11 interval 10

• Use the no version to stop the test that is running.
• See bert.

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

equipment loopback

• Use to enable or disable the router’s ability to enter into a loopback initiated by a remote device connected on a T3 interface.

  Note: Remote loopback is available only on frame-based T3 interfaces configured to use C-bit framing.

• Specify one of the following loopback options:
  • customer—Enables the router to enter into loopback when it receives an appropriate signal from the remote interface
  • network—Disables the router’s ability to enter into loopback when it receives an appropriate signal from the remote interface
• Examples

  host1(config-controll)#equipment customer loopback

  host1(config-controll)#equipment network loopback

• Use the no version to disable the router’s ability to be placed in loopback by the remote device.
• See equipment loopback.

loopback

• Use to configure a loopback.
• Specify one of the following loopback options:
  • local—Loops the data back toward the router; on supported line modules, also sends an alarm indication signal (AIS) out toward the network
  • network—Loops the data toward the network before the framer processes the data
  • payload—Loops the data toward the network after the framer processes the data
  • remote—Sends a far end alarm code in the C-bit framing, as defined in ANSI T1.404, to notify the remote end to activate or (when you use the no version) deactivate the line loopback

    Note: Remote loopback is available only on frame-based T3 interfaces configured to use C-bit framing.

• Example

  host1(config-controll)#loopback local

• Use the no version to restore the default configuration, no loopback.
• See loopback.