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Table Of Contents
Related Features and Technologies
Performing a BER Test on a T1 Line
Terminating a BER Test on a T1 Line
Verifying a BER Test on a T1 Line
Performing a BER Test on a DS3/E3 Interface
Terminating a BER Test on a DS3/E3 Interface
Verifying a BER Test on a DS3/E3 Interface
Monitoring and Maintaining BER Tests
Bit Error Rate Testing
This feature module describes how to configure a bit error rate test (BERT) and display the test results for channelized line cards in Cisco internet routers.
History for the Bit Error Rate Testing Feature
Finding Support Information for Platforms and Cisco IOS Software Images
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Contents
Feature Overview
Bit error rate test (BERT) circuitry is built into channelized line cards in Cisco internet routers and is supported on the following line cards:
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One-port Channelized OC-12 (DS3)
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Performing a BER Test
Bit error rate (BER) test allow you to test cables and diagnose signal problems in the field. You can configure individual T1 channel groups to run an independent BER test. You set one local serial port to Bit error rate test (BERT) mode while the remaining local serial ports continue to transmit and receive normal traffic. The BER test checks communication between the local and the remote ports.
When running a BER test, your system expects to receive the same pattern that it is transmitting. If traffic is not being transmitted or received, create a back-to-back loopback BER test on the link or in the network, and send out a predictable stream to ensure that you receive the same data that was transmitted.
To determine if the remote serial port returns the BERT pattern unchanged, you must manually enable network loopback at the remote serial port while you configure a BERT pattern to use in the test at specified time intervals on the local serial port.
You can later display and analyze the total number of error bits transmitted and the total number of bits received on the link. You can retrieve error statistics anytime during the BER test.
BERT Patterns Supported
Two categories of test patterns can be generated by the onboard BER test circuitry: pseudo-random and repetitive. Pseudo-random test patterns are exponential numbers and conform to the Consultative Committee on International Telephony and Telegraphy/International Telecommunications Union (CCITT/ITU) O.151 and O.153 specifications.
Table 1 describes the test patterns supported on channelized line cards in Cisco 12000 series Internet routers.
Table 1 BERT Patterns Supported in
Cisco 12000 Series Internet Routers
Benefits
Additional BERT Patterns Supported
Additional BERT patterns are now supported on channelized line cards in Cisco internet routers to allow you to test more thoroughly for bit errors on a T1 link and diagnose signal problems.
Restrictions
Only One T1/E1 BER Test Supported Per T3 Port
Only one BER test circuit is supported on the T1/E1 links configured for a T3 port.
T3 Links Not Supported
BER tests are not supported on a T3 link.
Two-Port Channelized OC-3/STM-1 Line Cards
When you perform BER tests on the DS1/E1 interface of a two-port channelized OC-3/STM-1 line card, the following restrictions apply:
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Four-Port Channelized OC-12/STM-4 Line Cards
When you perform BER tests on the DS3/E3 interface of a four-port channelized OC-12/STM-4 line card, the following restrictions apply:
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Six-Port Channelized T3 Line Cards
When you perform BER tests on the T1 interface of a six-port channelized T3 line card, the following restrictions apply:
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Related Features and Technologies
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Related Documents
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Configuration Tasks
This section describes how to configure and perform a BER test on a T1 line or a DS3 interface on a channelized line card, and how to stop or verify the test:
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Performing a BER Test on a T1 Line
Terminating a BER Test on a T1 Line
Router(config-controller)# no t1 line-number bert interval time
Terminates the BER test running on the specified T1 line.
Verifying a BER Test on a T1 Line
To verify that a BER test is running on a T1 line, enter the show controllers t3 slot/port:t1-line-number command at any time during the test.
Router# show controllers t3 6/0:1T3 6/0 is up. Hardware is GSR 6 port CT3T1 1 is uptimeslots: 1-24FDL per AT&T 54016 spec.No alarms detected.Framing is ESF, Clock Source is InternalBERT test result (running)Test Pattern : 2^11, Status : Sync, Sync Detected : 1Interval : 5 minute(s), Time Remain : 5 minute(s)Bit Errors (since BERT started): 6 bits,Bits Received (since BERT started): 8113 KbitsBit Errors (since last sync): 6 bitsBits Received (since last sync): 8113 Kbits
Performing a BER Test on a DS3/E3 Interface
Terminating a BER Test on a DS3/E3 Interface
Verifying a BER Test on a DS3/E3 Interface
To verify that a BER test is running on a DS3 interface, enter one of the following commands at any time during the test:
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show controllers sonet slot/port:sts1-number bert•
show controllers sonet slot/port:au3-number bert•
show controllers sonet slot/port:au4-number:vc3-number bertThe following example shows how to verify a BER test on a DS3 interface with SONET framing or SDH framing with AU-3 mapping:
Router# show controllers sonet 5/0:2 bertInterface Serial5/0:2 (DS3 channel 2)BERT information:State :enabled (sync'd)Pattern :2^15Interval :3 minuteTime remaining :00:00:30Total errors :5Time this sync :00:02:30Errors this sync :5Sync count :1
Monitoring and Maintaining BER Tests
To monitor a BER test on a channelized line card, use the following EXEC commands:
Configuration Examples
This section provides an example of how to send the BERT pseudo-random pattern of 2^20 through a T1 line 10 for five minutes.
Router(config)# controller T3 6/0
Router(config-controller)# t1 10 bert pattern 2^20 interval 5
Additional References
The following sections provide references related to bit error rate testing.
Standards
MIBs
None
To locate and download MIBs for selected platforms, Cisco IOS releases, and feature sets, use Cisco MIB Locator found at the following URL:
RFCs
Technical Assistance
Command Reference
This section documents modified commands only.
bert pattern interval
To perform a bit error rate test using a specified test pattern on a channelized interface on a Cisco 12000 series Internet routers, use the bert pattern interval command in global configuration mode. To disable BER testing, use the no form of this command.
[t1 line-number] [e1 line-number] bert pattern pattern interval time
no [t1 line-number] bert pattern pattern interval time
Syntax Description
t1 line-number
Optional. Configures a BER test on a T1 line under SONET or SDH framing by specifying the line number. Range: 1 to 28.
e1 line-number
Optional. Configures a BER test on an E1 line under SDH framing with AU-3 AUG mapping by specifying the line number. Range: 1 to 28.
bert pattern pattern
Specifies the DS1 test pattern to be used in the BER test. Valid values: 0s, 1s, 2^11, 2^15, 2^20, 2^23, alt-0-1, 1-8, and a user-defined value.
See Table 2 for a description of the patterns that are supported by each channelized interface.
interval time
Specifies the duration of the BER test in minutes. Range: 1 to 14400. (14400 minutes is equal to 240 hours.)
Defaults
No default behavior or values.
Command Modes
Global configuration
Command History
12.0(21)S
This command was introduced.
12.2(28)SB
This command was integrated into Cisco IOS Release 12.2(28)SB.
Usage Guidelines
You can configure only one BER test on a T3 port. If you start more than one test, the following error message is displayed:
%BERT is already running on T1 t1-line-number T3 port-number. Only one T1 bert test can be running at a time.The bit error rate test pattern occupies only the T1 or E1 payload bits.
You sometimes must enter a command prefix before the bert pattern interval command, depending on whether a T1 or E1 line uses SONET or Synchronous Digital Hierarchy (SDH) framing:
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Router(config)# controller sonet 6/0
Router(config-controller)# sts-1 1
Router(config-ctrrlr-sts1)# vtg 4 t1 1 bert pattern 2^11 interval 5•
Router(config)# controller sonet 6/0
Router(config-controller)# sts-1 1
Router(config-ctrrlr-sts1)# t1 1 bert pattern 2^11 interval 5•
Router(config)# controller sonet 6/0
Router(config-controller)# framing sdh
Router(config-controller)# aug mapping au-4
Router(config-controller)# au-4 1 tug-3 2
Router(config-ctrrlr-tug3)# mode c-12
Router(config-ctrrlr-tug3)# tug-2 4 e1 1 bert pattern 2^11 interval 5No command prefix is necessary when you configure a BER test on a serial E3 line or on a T1 line under Super Frame (SF) or Extended Superframe (ESF) framing.
Table 2 shows what BERT patterns are supported on each channelized line.
Table 2 BERT Patterns Supported on Channelized Lines
Examples
The following example shows how to run a BER test on a serial E3 line on a four-port Channelized OC-12/STM-4 line card:
Router# configure terminalRouter(config)# interface serial 5/0:2Router(config-if)# bert pattern 2^15 interval 3Router(config-if)# no bert pattern 2^15 interval 3The following example shows how to run a BER test on a T1 line under SF or ESF frame formatting on a six-port Channelized T3 line card:
Router# configure terminalRouter(config)# controller T3 6/0Router(config-if)# t1 bert pattern 2^20 interval 5The following example shows how to run a BER test on a T1 line under SONET framing on a two-port Channelized OC-3/STM-1 line card:
Router# configure terminalRouter(config)# controller sonet 6/0Router(config-controller)# sts-1 1Router(config-ctrlr-sts1)# vtg 2 bert pattern 2^11 interval 4The following example shows how to run a BER test on a T1 line under SDH framing with AU-3 AUG mapping on a two-port Channelized OC-3/STM-1 line card:
Router# configure terminalRouter(config)# controller sonet 6/0Router(config-controller)# au-3 1Router(config-ctrlr-au3)# tug-2 4 t1 1 bert pattern 2^11 interval 4The following example shows how to run a BER test on an E1 line under SDH framing with AU-4 AUG mapping on a two-port Channelized OC-3/STM-1 line card:
Router# configure terminalRouter(config)# controller sonet 6/0Router(config-controller)# au-4 tug-3 2Router(config-ctrlr-au3)# tug-2 4 e1 1 bert pattern 2^11 interval 4Related Commands
bert errors
Inserts a specified number of errors into the BERT pattern used in the BER test in progress.
show controllers
To display the results of a bit error rate test, use the show controllers command in priviliged EXEC mode.
show controllers [sonet slot/port.sts1-number/t1-number | sonet slot/port.sts1-number | vtg-number/t1-number | sonet slot/port.au-3-number/tug-2-number/t1-number |
sonet slot/port.au-4-number/tug-3-number/tug-2-number/e1-line-number |
sonet slot/port.au-4-number/vc3-number |
sonet slot/port:interface-number | t3 slot/port:t1-line-number] [bert | brief | tabular]Syntax Description
Command Modes
Priviliged EXEC
Command History
12.0(21)S
This command was introduced.
12.2(28)SB
This command was integrated into Cisco IOS Release 12.2(28)SB.
Usage Guidelines
You can enter the show controllers command at any time during a BER test:
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Examples
The following example shows sample output from the show controllers command for BERT results on a T1 line under SONET framing in VT-15 mode. (Table 3 describes the lines in the BER test portion of the output.)
Router# show controllers sonet 4/0.1/1/1 briefOC3.STS1 4/0.1 is up. Hardware is GSR 2 port STM1/OC3 (channelized)Applique type is VT1.5 in STS-1STS-1 1, VTG 1, T1 1 (VT1.5 1/1/1) is uptimeslots: 1-24FDL per AT&T 54016 spec.No alarms detected.Framing is ESF, Clock Source is InternalBERT test result (running)Test Pattern : 2^20-QRSS, Status : Sync, Sync Detected : 1Interval : 5 minute(s), Time Remain : 4 minute(s)Bit Errors (since BERT started): 0 bits,Bits Received (since BERT started): 112 MbitsBit Errors (since last sync): 0 bitsBits Received (since last sync): 112 MbitsTable 3
show controllers sonet Line Descriptions
The next example shows sample output from the show controllers command for BERT results on an E1 line under SDH framing with AU-4 AUG mapping.
Router# show controllers sonet 3/0.1/3/5SONET 3/0 is up. (Configured for Locally Looped) Hardware is GSR 2 portSTM1/OC3 (channelized)Applique type is Channelized OCx interfaceClock Source is Line, AUG mapping is AU4.Medium info:Type: SDH, Line Coding: NRZ, Line Type: Short SMRegenerator Section:LOF = 0 LOS = 0 BIP(B1) = 0Multiplex Section:AIS = 0 RDI = 0 REI = 0 BIP(B2) = 0Active Defects: NoneActive Alarms: NoneAlarm reporting enabled for: SF SLOS SLOF B1-TCA B2-TCA B3-TCABER thresholds: SF = 10e-3 SD = 10e-6TCA thresholds: B1 = 10e-6 B2 = 10e-6 B3 = 10e-6High Order Path:PATH 1:AIS = 0 RDI = 0 REI = 15 BIP(B3) = 11LOP = 0 PSE = 4 NSE = 0 NEWPTR = 1LOM = 0 PLM = 0 UNEQ = 0Active Defects: NoneS1S0 = 02, C2 = 02PATH TRACE BUFFER : STABLECRC-7: 0xF2 OK52 6F 75 74 65 72 33 2F 30 2F 31 00 00 00 00 Router3/0/1....STM1.AU4 3/0.1 is up. Hardware is GSR 2 port STM1/OC3 (channelized)Applique type is C12 in TUG-3 in AU-4AU-4 1, TUG-3 1, TUG-2 1, E1 1 (C-12 1/1/1/1) is uptimeslots: 1-31No alarms detected.Framing is crc4, Clock Source is InternalBERT test result (running)Test Pattern : 2^15, Status : Sync, Sync Detected : 1Interval : 5 minute(s), Time Remain : 5 minute(s)Bit Errors (since BERT started): 0 bits,Bits Received (since BERT started): 95 MbitsBit Errors (since last sync): 0 bitsBits Received (since last sync): 95 MbitsData in current interval (708 seconds elapsed):0 Line Code Violations, 1 Path Code Violations0 Slip Secs, 1 Fr Loss Secs, 0 Line Err Secs, 0 Degraded Mins1 Errored Secs, 0 Bursty Err Secs, 0 Severely Err Secs0 Unavail Secs, 0 Stuffed SecsData in Interval 1:0 Line Code Violations, 0 Path Code Violations0 Slip Secs, 0 Fr Loss Secs, 0 Line Err Secs, 0 Degraded Mins0 Errored Secs, 0 Bursty Err Secs, 0 Severely Err Secs0 Unavail Secs, 0 Stuffed SecsData in Interval 2:0 Line Code Violations, 0 Path Code Violations0 Slip Secs, 0 Fr Loss Secs, 0 Line Err Secs, 0 Degraded Mins0 Errored Secs, 0 Bursty Err Secs, 0 Severely Err Secs0 Unavail Secs, 0 Stuffed SecsData in Interval 3:0 Line Code Violations, 0 Path Code Violations0 Slip Secs, 1 Fr Loss Secs, 0 Line Err Secs, 0 Degraded Mins1 Errored Secs, 0 Bursty Err Secs, 0 Severely Err Secs0 Unavail Secs, 0 Stuffed SecsTotal Data (last 3 15 minute intervals):0 Line Code Violations,0 Path Code Violations,0 Slip Secs, 1 Fr Loss Secs, 0 Line Err Secs, 0 Degraded Mins,1 Errored Secs, 0 Bursty Err Secs, 0 Severely Err Secs0 Unavail Secs, 0 Stuffed SecsThe third example shows sample output from the show controllers command for BERT results on a T1 line under ESF framing:
Router# show controllers sonet 3/0.1/3/5Router# show controller t3 6/0:1T3 6/0 is up. Hardware is GSR 6 port CT3T1 1 is uptimeslots: 1-24FDL per AT&T 54016 spec.No alarms detected.Framing is ESF, Clock Source is InternalBERT test result (running)Test Pattern : 2^11, Status : Sync, Sync Detected : 1Interval : 5 minute(s), Time Remain : 5 minute(s)Bit Errors (since BERT started): 6 bits,Bits Received (since BERT started): 8113 KbitsBit Errors (since last sync): 6 bitsBits Received (since last sync): 8113 KbitsRelated Commands
show version
Displays information about the router's hardware and software configuration.
Glossary
6CT3-SMB—Product number of the 6-port channelized DS3 line card for Cisco 12000 series Internet routers that supports packet over DS1.
BERT—Bit error rate test. Bit error rate is the probability that a bit error could occur on any given bit on a line.
CLI—Cisco IOS command-line interface.
CT3—Channelized T3.
DS1—Digital Signal Level 1. A U.S. standard for high-speed data transmission over a T1 line at a data rate of 1.544 Mbits/sec.
DS3—Digital Signal Level 3. A U.S. standard for high-speed data transmission over a T3 line at a data rate of 44.736 Mbits/sec.
T1—A digital carrier facility used to transmit a DS1-formatted digital stream at 1.544 Mbps.
T3—A digital carrier facility used to transmit a DS3-formatted digital stream at 44.746 Mbps.
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