# Testing Interfaces

If you want to run loopback tests or bit error rate tests on channelized T3 interfaces, you must enable testing at the T3 or T1 layer. See Interface Stack for a description of the layers.

For a list of the modules that support bit error rate tests (BERTs) and remote loopback, see ERX Module Guide, Appendix A, Module Protocol Support.

| Note: BERTs are supported on frame-based channelized T3 interfaces, with the exception of the CT3/T3 line module used with the 3-port CT3/T3 I/O module.

## Testing at the T3 Layer

To enable testing at the T3 layer:

1. Change the clock source to internal.
   host1(config-controll)#clock source internal module
2. Configure one of the following tests:
   - Set the loopback to local to test the line without connecting to the network.
     host1(config-controll)#loopback local
   - Set the loopback to network to test the line connected to the network.
     host1(config-controll)#loopback network line
3. (Optional) Configure one of the following tests for remote loopback:
   - 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
4. Configure the line to run bit error rate tests.
   host1(config-controll)#bert pattern 2^15 time 20

bert

- Use to enable bit error rate tests using the specified pattern on a channelized 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 2^15 interval 20
- Use the no version to stop the test that is running.
- See bert.

equipment loopback

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

  | Note: Remote loopback is available only on channelized 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 channelized 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.

## Testing at the T1 Layer

The T1 channel testing commands enable you to specify testing parameters for a single channel, multiple individual channels, ranges of channels, or any combination of the three types of specifications. For example:

host1(config-controll)#t1 3,6-15,22,25-27 loopback local

To enable testing at the T1 layer:

1. Configure one of the following loopback tests.
   - Set the loopback to local to test the line without connecting to the network.
     host1(config-controll)#t1 2 loopback local
   - Set the loopback to network to test the line connected to the network.
     host1(config-controll)#t1 2 loopback network line
   - Set the loopback to remote-loopback to enable acceptance of loopback commands issued from a remote router.
     host1(config-controll)#t1 2 remote-loopback
2. Configure the line to run bit error rate tests.
   host1(config-controll)#t1 2 bert pattern 2^11 time 10 unframed

t1 bert

- Use to enable bit error rate tests using the specified pattern on a T1 interface.
- Unlike other configuration commands, bert is not stored in NVRAM.
- Specify one of the following test patterns:

  | Note: The CT3/T3-F0 line module supports only the 2^11, 2^15, and 2^20-O153 options.

  - 0s—Repetitive test pattern of all zeros, 00000...
  - 1s—Repetitive test pattern of all ones, 11111...
  - 2^11—Pseudorandom test pattern, 2047 bits in length
  - 2^15—Pseudorandom test pattern, 32,767 bits in length
  - 2^20-O153—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...

    | Note: The BERT patterns supported when testing the T1 layer vary depending on the line module and I/O module assembly you are using.

- Specify the duration of the test in the range 1–1440 minutes.
- Optionally, specify the unframed keyword to overwrite the framing bits.
- Example
  host1(config-controll)#t1 2 bert pattern 2^11 interval 10 unframed
- Use the no version to stop the test that is running.
- See t1 bert.

t1 loopback

- Use to configure a loopback.
- Specify one of the following options:

  | Note: The CT3/T3-F0 line module does not support the remote line inband option.

  - local—Loops the router output data back toward the router at the T1 framer; on supported line modules, also sends an alarm indication signal (AIS) out toward the network
  - network { line | payload }—Specify the line keyword to loop the data back toward the network before the T1 framer and automatically set a local loopback at the HDLC controllers. Specify the payload keyword to loop the payload data back toward the network at the T1 framer and automatically set a local loopback at the HDLC controllers.
  - remote line fdl ansi—Sends a repeating 16-bit ESF data link code word (00001110 11111111) to the remote end requesting that it enter into a network line loopback. Specify the ansi keyword to enable the remote line facilities data link (FDL) ANSI bit loopback on the T1 channel, according to the ANSI T1.403 Specification.
  - remote line fdl bellcore—Sends a repeating 16-bit ESF data link code word (00010010 11111111) to the remote end requesting that it enter into a network line loopback. Specify the bellcore keyword to enable the remote line facilities data link (FDL) Bellcore bit loopback on the T1 channel, per the Bellcore TR-TSY-000312 Specification.
  - remote line inband—Sends a repeating 5-bit inband pattern (00001) to the remote end requesting that it enter into a network line loopback
  - remote payload [ fdl ] [ ansi ]—Sends a repeating, 16-bit, ESF data link code word (00010100 11111111) to the remote end requesting that it enter into a network payload loopback. Enables the remote payload facilities data link (FDL) ANSI bit loopback on the T1 channel. You can optionally specify fdl and ansi.
- If you do not specify an option, the router will set a local loopback for the channel.
- Example
  host1(config-controll)#t1 2 loopback local
- Use the no version to deactivate loopback. If you specify the remote keyword, the no version sends the 16-bit ESF data link code word or inband pattern to deactivate the loopback at the remote end based on the last activate request sent to the remote end. If you do not specify the remote keyword, the no version clears the local loopback configuration.
- See t1 loopback.

t1 remote-loopback

- Use to enable the acceptance of loopback commands issued from a remote router.
- Example
  host1(config-controll)#t1 2 remote-loopback
- Use the no version to restore the factory default, which is to reject loopback commands issued from a remote router.
- See t1 remote-loopback.