Configuration Guide for Cisco NCS 1004, IOS XR Release 25.x.x

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Configuration Guide for Cisco NCS 1004, IOS XR Release 25.x.x

Pseudo-random binary sequence

Updated: July 31, 2026

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This section explains how pseudo-random binary sequences (PRBS) enable data integrity checks on NCS 1002 and NCS 1004 trunk links without enabling client traffic.

A pseudo-random binary sequence is a diagnostic signal pattern that

  • enables rigorous data integrity checks between trunk links (such as NCS 1002 and NCS 1004) without enabling typical client traffic,

  • supports configurable transmission and reception modes to simulate traffic and detect errors, and

  • provides multiple sequence patterns and operational modes to test and monitor link performance under various conditions.

Table 1. Feature history

Feature Name

Release Information

Feature Description

PRBS (Pseudo Random Binary Sequence) on ODU4

Cisco IOS XR Release 7.3.1

1.2T card supports PRBS on the ODU4 controller. This feature allows you to test whether the traffic is error free during link bring up without depending on the peer port.

The Pseudo Random Binary Sequence (PRBS) feature allows you to perform data integrity checks between the NCS 1002 trunk links without enabling actual client traffic.

The Pseudo Random Binary Sequence (PRBS) feature allows you to perform data integrity checks between the NCS 1004 trunk links without enabling actual client traffic.

You must enable the PRBS feature on both the transmitting and receiving NCS 1004 trunk ports. The transmitting trunk port generates a bit pattern and sends it to the peer NCS 1004 device. The device detects whether it receives the sent bit pattern.

PRBS modes on the 1.2T card

From Release 7.3.1, you can configure PRBS on the NCS 1004 trunk port for the 2-QDD-C card.

You can configure the NCS 1002 trunk port in one of these modes for PRBS on the 1.2T card:

You can configure the NCS 1004 trunk port in one of these modes for PRBS on the 1.2T card:

  • Source mode — The NCS 1002 NCS 1004 at trunk port generates PRBS signal on the line continuously as per the configured PRBS pattern.

  • Sink mode — The NCS 1002 NCS 1004 at trunk port gets locked to the ingress signal according to the configured pattern, analyzes and reports the errors.

  • Source-Sink mode — The NCS 1002 NCS 1004 at trunk port acts as both the PRBS transmitter and receiver, that is, it generates PRBS signal as per the configured pattern, and also gets locked to the ingress signal with the same pattern, and reports the errors.

Note

From Release 7.3.1, the 1.2T card supports PRBS on ODU4.

PRBS patterns on NCS 1004 trunk ports

The NCS 1004 trunk port supports these PRBS patterns:

  • PRBS31 — Sequence length is from 2^31 -1 bits.

  • PRBS23 — Sequence length is from 2^23 -1 bits.

  • PRBS15 — Sequence length is from 2^15 -1 bits.

  • PRBS11 —Sequence length is from 2^11 -1 bits.

  • PRBS7 —Sequence length is from 2^7 -1 bits.

Note

For higher data rates such as 100G and 400G, we recommend that you

  • use high-sequence-length PRBS patterns, and

  • use the PRBS inverted pattern.

Alarms are not visible on the trunk ports when PRBS is enabled.

PRBS limitations

The PRBS feature has these limitations:

  • SNMP does not support fetching the PRBS status or performance monitoring (PM) data.

  • PRBS does not support 30-second current or historical PM data.

  • PRBS PM TCAs are not supported.

  • TTI functionality is not supported with PRBS.

  • Loopback and PRBS configurations cannot coexist on a coherentDSP controller. The system rejects a loopback configuration if PRBS is already configured.

  • Apply the PRBS configuration only after the coherentDSP upgrade is complete.

  • PRBS on ODU4 is supported only when the slice is provisioned in OTN client mode.

PRBS on the OTN-XP card

From Release 7.2.1, the OTN-XP card supports PRBS on the mapper optical data unit (ODU2e).

Note

ODU2e PRBS is not supported for OTU2E client rates.

The NCS 1004 trunk port with the OTN-XP card supports these PRBS modes and the invertedpn31 pattern:

  • Source mode — The NCS 1004 at trunk port generates PRBS signal on the line continuously as per the configured PRBS pattern.

  • Sink mode — The NCS 1004 at trunk port gets locked to the ingress signal according to the configured pattern, analyzes and reports the errors.

  • Source-Sink mode — The NCS 1004 at trunk port acts as both the PRBS transmitter and receiver, that is, it generates PRBS signal as per the configured pattern, and also gets locked to the ingress signal with the same pattern, and reports the errors.

  • invertedpn31 —Inverted pattern. Sequence length is from 2^31 -1 bits.

The NCS 1004 trunk port supports these PRBS patterns:

  • PRBS31 — Sequence length is from 2^31 -1 bits.

  • PRBS23 — Sequence length is from 2^23 -1 bits.

  • PRBS15 — Sequence length is from 2^15 -1 bits.

  • PRBS7 —Sequence length is from 2^7 -1 bits.

Configure PRBS on OTN-XP card

Enable PRBS mode on ODU controllers to support advanced diagnostics for OTN-XP cards.

To configure PBRS mode on the ODU2e controller, you must configure Optical Channel Payload Unit (OPU) on the ODU2e controller followed by the PRBS mode and the pattern. The PRBS supported pattern on the OTN-XP card is invertedPN31.

From Release 7.3.1, you can configure PRBS on client or mapper ODU4 and ODU flex controllers.

For fiber channel controllers, PRBS is supported on mapper ODU flex controllers.

Note

ODU2e PRBS is not supported for OTU2E client rates.

Follow these steps to configure PRBS mode on the ODU2e controller:

Procedure

1.

Run the configure controller odu2e | oduflexR/S/I/P/client-port/lane-number secondary-admin-state maintenance opu prbs mode{source | sink | source-sink} pattern invertedpn31 {direction {system | line}} command to configure PRBS mode on the ODU2e controller.

Example:

This example shows how to configure PRBS mode as source-sink with pattern as invertedpn31:


RP/0/RP0/CPU0:ios#configure
RP/0/RP0/CPU0:ios(config)#controller odu2e0/2/0/12/3/2   
RP/0/RP0/CPU0:ios(config-odu2e)#secondary-admin-state maintenance
RP/0/RP0/CPU0:ios(config-odu2e)#opu
RP/0/RP0/CPU0:ios(config-Opuk)#prbs mode source-sink pattern invertedpn31
RP/0/RP0/CPU0:ios(config-Opuk)#end
RP/0/RP0/CPU0:ios(config-odu2e)#commit
2.

Run the show controller odu2e command to verify the configuration.

Example:

This is a sample output of show controller odu2e command.

RP/0/RP0/CPU0(config-odu2e)#show controller odu2e 0/2/0/12/3/2 prbs-details 
Mon Mar 14 21:33:02.293 UTC

 -------------------------PRBS details----------------------------------
PRBS Test                       : Enable
PRBS Mode                       : Source-Sink
PRBS Pattern                    : INVERTED PN31
PRBS Status                     : Locked
PRBS Lock Time(in seconds)      : 1190
PRBS Bit Errors                 : 0
---------------------------------------------------

This example shows how to configure PRBS mode as source-sink with pattern as invertedpn31 with direction as system:


RP/0/RP0/CPU0:ios#configure
Wed Nov 11 00:38:11.789 UTC
RP/0/RP0/CPU0:ios(config)#controller odu4 0/2/0/5
RP/0/RP0/CPU0:ios(config-odu4)#secondary-admin-state maintenance
RP/0/RP0/CPU0:ios(config-odu4)#opu prbs mode source-sink pattern invertedpn31 direction system
RP/0/RP0/CPU0:ios(config-odu4)#commit
Wed Nov 11 00:38:26.391 UTC

This example shows how to configure PRBS mode as source-sink with pattern as invertedpn31 with direction as line:


RP/0/RP0/CPU0:ios#configure
Wed Nov 11 00:38:11.789 UTC
RP/0/RP0/CPU0:ios(config)#controller odu4 0/2/0/5
RP/0/RP0/CPU0:ios(config-odu4)#secondary-admin-state maintenance
RP/0/RP0/CPU0:ios(config-odu4)#opu prbs mode source-sink pattern invertedpn31 direction line
RP/0/RP0/CPU0:ios(config-odu4)#commit
Wed Nov 11 00:38:26.391 UTC

This example shows how to configure PRBS on the mapper controller:


RP/0/RP0/CPU0:ios#configure
Thu Oct 7 13:17:27.267 UTC
RP/0/RP0/CPU0:ios(config)#controller odu4 0/2/0/13/8
RP/0/RP0/CPU0:ios(config-odu4)#secondary-admin-state maintenance
RP/0/RP0/CPU0:ios(config-odu4)#opu prbs mode source-sink pattern invertedpn31
RP/0/RP0/CPU0:ios(config-odu4)#commit

This example shows how to configure PRBS on the mapper controller with PRBS mode as source-sink and pattern as invertedpn31 with direction as line:


RP/0/RP0/CPU0:ios(config)#controller odu4 0/3/0/7
RP/0/RP0/CPU0:ios(config-odu4)#secondary-admin-state maintenance
RP/0/RP0/CPU0:ios(config-odu4)#opu prbs mode source-sink pattern invertedpn31 direction line
RP/0/RP0/CPU0:ios(config-odu4)#commit
Tue Oct 12 13:17:07.840 UTC

PRBS is configured on the ODU controller.

Verify PRBS on OTN-XP card

Ensure proper PRBS test configuration and signal synchronization to maintain optical transmission integrity on ODU controllers for OTN-XP cards.
Follow these steps to verify PRBS status on ODU controllers for OTN-XP cards:

Procedure

Run the show controllers odu2e R/S/I/P/client-port/client-lane prbs-details to verify the PRBS status.

Example:

This example displays the output of the PRBS configuration with PRBS mode as sink.


RP/0/RP0/CPU0:ios#show controllers odu2e 0/2/0/12/3/2 prbs-details 
-------------------------PRBS details----------------------------------
PRBS Test               : Enable
PRBS Mode               : Sink
PRBS Pattern            : INVERTED PN31
PRBS Status             : Locked

This example displays the output of the PRBS configuration with PRBS mode as source-sink.


RP/0/RP0/CPU0:ios#show controllers odu2e 0/2/0/12/3/2 prbs-details 
-------------------------PRBS details----------------------------------
PRBS Test               : Enable
PRBS Mode               : Source-Sink
PRBS Pattern            : INVERTED PN31
PRBS Status             : Locked

This example displays the output of the PRBS configuration on the mapper controller.


RP/0/RP0/CPU0:ios#show controllers odu4 0/2/0/13/8 prbs-details
Thu Oct 7 13:21:19.444 UTC

-------------------------PRBS details----------------------------------
PRBS Test : Enable
PRBS Mode : Source-Sink
PRBS Pattern : INVERTED PN31
PRBS Status : Locked

---------------------------------------------------

This example displays the output of the PRBS configuration on the mapper controller with PRBS mode as source-sink and pattern as invertedpn31 with direction as line.


RP/0/RP0/CPU0:ios#show controllers odu4 0/3/0/7 prbs-detailsTue Oct 12 13:17:22.748 UTC
Tue Oct 12 13:17:22.748 UTC
-------------------------PRBS details----------------------------------
PRBS Test : Enable
PRBS Mode : Source-Sink
PRBS Pattern : INVERTED PN31
PRBS Status : Unlocked
PRBS Direction : Line
PRBS Bit Errors : 0

---------------------------------------------------

The PRBS Status field shows Locked when PRBS is active and the signal is synchronized. The PRBS Bit Errors field shows the number of errors detected.

Clear bit errors and lock time for PRBS

Ensure an accurate PRBS test by removing previous bit errors and lock time before testing.

Lock time is the time that is elapsed since the last PRBS lock is detected.

Follow these steps to clear PRBS bit errors and lock time:

Procedure

1.

Run the show controllers command to verify the current PRBS status to check for bit errors.

Example:

This sample shows that bit errors are observed during the PRBS test. 


RP/0/RP0/CPU0:ios#show controllers odu4 0/2/0/5 prbs-details
Fri Nov 13 03:21:44.191 UTC

-------------------------PRBS details----------------------------------
PRBS Test : Enable
PRBS Mode : Source-Sink
PRBS Pattern : INVERTED PN31
PRBS Status : Locked
PRBS Direction : Line
PRBS Lock Time(in seconds) : 28
PRBS Bit Errors : 23776

---------------------------------------------------
2.

Run the clear controller command to clear the lock time and bit errors before the PRBS test.

Example:


RP/0/RP0/CPU0:ios#clear controller odu4 0/2/0/5 prbs-details
Fri Nov 13 03:21:50.726 UTC
PRBS bit errors cleared

This sample displays the bit errors and lock time are removed.


RP/0/RP0/CPU0:ios#show controllers odu4 0/2/0/5 prbs-details
Fri Nov 14 03:21:44.191 UTC
-------------------------PRBS details----------------------------------
PRBS Test : Enable
PRBS Mode : Source-Sink
PRBS Pattern : INVERTED PN31
PRBS Status : Locked
PRBS Direction : Line
PRBS Lock Time(in seconds) : 2
PRBS Bit Errors : 0

The PRBS bit errors and lock time are cleared. The PRBS Bit Errors field shows 0 and the lock time is reset.