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Troubleshooting

Troubleshooting

The MGX 8260 Media Gateway includes diagnostic features that facilitate fault location, such as loopback and bit error rate tests. See the following sections for information on how to locate and clear trouble conditions.

Performing Loopback Tests

Loopback tests are powerful troubleshooting tools that help maintenance personnel locate faults along the transmission path. DS1/E1 and DS3 lines provide both local and line loopbacks.


Figure 8-1: DS1/E1 and DS3 Loopback Options


The local loopback option loops the DS1 signal back towards the backplane and helps isolate problems on the MGX 8260 side of the signal path. The line loopback option loops the signal back towards the DS1 or DS3 line and helps identify problems in the signal path between the MGX 8260 Media Gateway and other network equipment. A third option, payload loopback, is similar to line loopback, except that the RX signal loops through the card's DS1 or DS3 framer logic before being returned on the TX line. Payload loopback helps determine whether the card itself is functioning properly.

Warning Loopback testing interrupts service. Perform during in a pre-arranged maintenance window or when the line is down.

DS1/E1 Loopback

To perform a DS1/E1 loopback test, follow these steps:

Step 1   Activate the loopback using the chds1ln. Specify the first and last parameters—the slot and line number, delimited by a period, of the DS1 line and the type of loopback test. Refer to the following table for loopback types:

Value Name

1

dsx1NoLoop

2

dsx1PayloadLoop

3

dsx1LineLoop

4

dsx1OtherLoop (local)

For example, the following command loops line 2 on slot 3:

chds1ln 3.2 # # # # 2

The system activates the loopback and changes the corresponding line LED to blinking yellow.

Step 2   Perform DS1/E1 signal tests, such as the BERT test. For more information, see the "Performing BERT Tests" section.

Step 3   Release the loopback by entering the chds1ln command again, but specify the dsx1NoLoop parameter. For example, to release the loopback on slot 3, line 2, enter the command as follows:

chds1ln 3.2 # # # # 1

The system releases the loopback, changes the line LED to green, and returns the line to normal operation.

Step 4   Verify that the loopback is clear using the lsds1ln command.

DS3 Loopback

To perform a DS3 loopback test, follow these steps:

Step 1   Activate the loopback using the chds3ln command. Specify the first and last parameters—the slot and line number, delimited by a period, of the DS1 line and the type of loopback test. Refer to the following table:

Value Name

1

dsx3NoLoop

2

dsx3PayloadLoop

3

dsx3LineLoop

4

dsx3OtherLoop

Note   Local loopback for DS3 lines is not supported.

For example, the following command loops line 2 on slot 7:

chds1ln 7.2 # # # # 2

The system activates the loopback and changes the corresponding line LED to blinking yellow.

Step 2   Perform DS3 signal tests, as appropriate.

Step 3   Release the loopback by reentering the chds3ln command, but specify the dsx3NoLoop parameter. For example, to release the loopback on slot 7, line 2, enter the command as follows:

chds3ln 7.2 # # # # 1

The system releases the loopback, changes the line LED to green, and returns the line to normal operation.

Step 4   Verify that the loopback is clear using the lsds3ln command.

SONET Loopback

To perform a SONET loopback test, follow these steps:

Step 1   Activate the loopback using the chsonetln command, specifying the slot, line, and loopback type. Refer to the following table for the loopback type:

Value Name

1

No loop

2

Line loop

3

Serial loop

4

Parallel loop

Note   Serial and parallel loops are both local loopback states.

For example, the following command loops line 2 on slot 9:

chsonetln 9.2 # # # 2

The system activates the loopback and changes the corresponding line LED to blinking yellow.

Step 2   Perform SONET signal tests, as appropriate.

Step 3   Release the loopback by reentering the chds3ln command, but specify the dsx3NoLoop parameter. For example, to release the loopback on slot 7, line 2, enter the command as follows:

chsonetln 7.2 # # # # 1

The system releases the loopback, changes the line LED to green, and returns the line to normal operation.

Step 4   Verify that the loopback is clear using the lssonetln command.

Performing BERT Tests

Bit Error Rate Tests (BERT) check the error performance of DS1/E1 lines. Often used in conjunction with loopback tests, this test helps isolate equipment or line segments with degraded performance. Typically, you activate loopback on one end of the communications link and activate the BERT test on the other. Do not activate loopback and BERT together on the same equipment.

Warning BERT tests interrupt service. Perform in a pre-arranged maintenance window or when the line is down.

DS1/E1 BERT Test

To use the DS1/E1 BERT test, follow these steps:

Step 1   Activate the test signal using the onbertds1 command as described in the "onbertds1" section. For example, the following command activates the bert test on channel 1 of line 1 in slot 11 using a rand9Bit pattern with no error injection.

onbertds1 11.1 1 1 1

Step 2   Check the test results using the lsbertds1 command, specifying the slot and line number, delimited by a period, of the DS1 line.

The system displays the BERT status:

======================================================================= DS1 Bert Status (lsbertds1) ======================================================================= DS1 Line : 11.1 Bert Status : inSync Received Bit Pattern : 4050854036 Receive Count : 9345256 Receive Error Count : 0

Displayed Information Description

DS1 Line

The line for the test results.

Bert Status

The status of the test, as follows:

1: idle

2: in-sync

3: out-of-sync

4: failed

Received Bit Pattern

The bit pattern the receiver synchronized on.

Receive Count

The number of bits received during the BERT test. Use this parameter with the Receive Error Count to calculate the Bit Error Rate (BER).

Receive Error Count

The number of error bits received during the BERT test. Use this parameter with the Receive Count to calculate the Bit Error Rate (BER).

Step 3   Stop the test using the offbertds1 command, specifying the slot and line number. For example:

offbertds1 11.1

The system stops the bert test and resumes transport of normal traffic.

Clearing Alarms

The MGX 8260 Media Gateway has the following alarm categories:

If you know the alarm source, proceed to the corresponding section of this chapter. Otherwise, start at the shelf level and work toward the cause.

Clearing Chassis Alarms

Chassis alarms report the state of chassis environmental sensors, fan speed, card state, and 48 supply status.

To view chassis alarms, follow these steps:

Step 1   Enter the lsalms command.

The system displays a summary of environmental, card, and software alarms.

Step 2   Use the information to identify the most severe alarm.

Step 3   Clear the most severe alarm.

Step 4   If the system alarm identifies a card, follow instructions in "Clearing Card Alarms".

Clearing Card Alarms

Card alarms pertain to functions that affect general card operation. To view card alarms, enter the lscd command, specifying the card number.

The system displays information about the card, including alarm and failure details. Using the integrated alarm field described in the following table, find the description that matches your problem, and follow the instructions:

Displayed Information Description

Integrated line alarm

One of the lines raised an alarm. Follow the instructions in section of this chapter that describes the type of line.

Line performance alarm

One of the lines raised a performance alarm. Follow the instructions in section of this chapter that describes the type of line.

Integrated port alarm

One of the ports raised an alarm. Check the port configuration and make necessary changes.

EMM temperature alarm

A temperature sensor raised an environmental alarm. Follow instructions in the "Clearing Environmental Alarms" section.

EMM voltage alarm

A voltage sensor raised an environmental alarm. Follow instructions in the "Clearing Environmental Alarms" section.

Component failure alarm

A hardware component of the card failed. Try the following possible remedies:

  • Reset the card and check to see if the alarm clears.

  • Remove and replace the card.

Clearing DS1/E1 and DS3 Alarms

The MGX 8260 Media Gateway supports DS1 and DS3 physical layer alarm signalling. To view current DS1 alarm conditions, enter the lsds1lns command. To view current DS3 alarms, enter the lsds3lns command.

The system lists a summary of line type, code, status, and signal code for each line. Use the Line Status field and the following guidelines to clear an alarm.

Displayed Information Possible Cause and Corrective Action

LOF

A Loss of Frame alarm occurs when the MGX 8260 cannot synchronize on frames. Try the following possible remedies:

  • Verify that the framing format and clock settings for the line match the port settings.

  • Check the statistics for the line and look for abnormally high error rates.

  • If the line appears to have problems, use loopback tests to diagnose the condition.

LOS

A Loss of Signal alarm occurs when the MGX 8260 cannot detect a signal at the line. Try the following possible remedies:

  • Check for obvious physical cable damage, tight bends, or other unusual conditions.

  • If the line appears to have problems, use loopback tests to diagnose the condition.

AIS

An Alarm Indication Signal (0/1 pattern) occurs when the receive link encounters problems for a set number of frames.

RDI

A Remote Defect Indication occurs when the remote equipment encounters problems for a set number of frames at that layer.

LOMF (E1 only)

Check for framing format misconfiguration

Check for CRC bits errors in the frame

Check for line coding misconfiguration

LOSMF (E1 only)

  • Check for framing format misconfiguration

  • Check for TS16 alteration

  • Check for bit errors in TS16

  • Check for line coding misconfiguration

Yellow (RAI)

  • Check the transmit on the near end

  • Check the physical connection

  • Perform a BERT to verify the line condition

RMAI (E1 only)

  • Check the transmit of TS16 at the near end

  • Check the physical connection

  • Perform a BERT to verify the line condition

Red Alarm
(LOS or LOF)

See LOS of LOF above.

Yellow Alarm
(RAI or RMAI)

See RAI or RMAI above.

Use the following guidelines to solve general DS1/E1 configuration problems.

Problem Possible Cause

Failure to configure CAS

  • D-channel is enabled

  • Framing format conflict

Failure to change framing type

  • D-channel is enabled

  • Failure to set hardware device

Failure to delete a line

  • Voice port exists

  • Hardware failure

Failure to change system line interface mode

  • BSC configured, even if not physically installed, when changing from the T1 to E1 mode

  • T1 line exists when changing from the T1 to E1 mode

  • E1 line exists when changing from the E1 to T1 mode

Clearing Fast Ethernet Alarms

The MGX 8260 Media Gateway monitors the Fast Ethernet trunks for conditions that can cause service interruption. To view Fast Ethernet line state, enter the lsethlns command.

The system displays a summary of the trunk status, including the Operational Status for each line. Respond to alarms depending on the displayed alarm indication as shown in the following table:

Displayed Information Possible Cause and Corrective Action

Failed

The Fast Ethernet failed. Make sure the SCC is in the standby mode and replace the card.

Link down in active state

The Fast Ethernet carrier is down. Try the following possible remedies:

  • Check the corresponding Fast Ethernet cable at the rear of the MGX 8260 chassis. It should be fully inserted and snapped in place.

  • Trace the Fast Ethernet network, checking for faults in other network components.

Link down in inactive state

The Fast Ethernet carrier is down, but the link is inactive. Try the following possible remedies:

  • Check for network administration or maintenance activity on the Fast Ethernet.

  • Check the corresponding Fast Ethernet cable at the rear of the MGX 8260 chassis. It should be fully inserted and snapped in place.

  • Trace the Fast Ethernet network, checking for faults in other network components.

Clearing SONET Alarms

The MGX 8260 Media Gateway continuously monitors lines for defect conditions and integrates alarm events over time. An alarm is declared when the defect persists for 2 seconds, and is cleared when the alarm is absent for 10 seconds. Alarm changes generate traps that notify managers of the state change.

To view alarms, use the lssonetstat command.

Respond to major alarms according to the guidelines in the following table:

Major Alarm Corrective Action

LOS

  • Verify the physical connection (cables, connectors) in the receive direction

  • Verify that the OC3 line on remote node is transmitting

OOF

  • Verify that incoming signal is OC3

  • Verify that the MGX8260 and remote node use to the same clock source

LOP-P

  • Verify that the incoming signal is OC3 with STS3c frame structure

  • Verify that the SONET frame scrambling is enabled on both sides

Respond to minor alarms according to the guidelines in the following table:

Minor Alarm Corrective Action1

AIS-L

The problem originated from an upstream node; investigate nodes in upstream direction

RFI-L

  • Activate a line loopback at the remote node and isolate problem by checking the looped signal

  • Verify the physical connection (cables and connectors) in the MGX 8260 Media Gateway transmit direction

AIS-P

The problem originated from an upstream node; investigate nodes in upstream direction

RFI-P

  • This is ok if MGX 8260 Media Gateway is currently transmitting AIS-P to the remote node

  • Otherwise, check for conditions on MGX 8260 Media Gateway that could lead to LOP-P on the remote side

TIM-P

  • Verify that the expected path trace identifier (J1) is configured properly

  • Investigate why the remote node is transmitting a path trace identifier that does not match the expected value

UNEQ-P

  • Verify that the remote node has the signal label (C2) byte configured properly

  • Investigate why the remote node is transmitting a signal label that does not match the expected value

PLM-P

  • Verify that the remote node has the signal label (C2) byte configured properly

  • Investigate why the remote node is transmitting a signal label that does not match the expected value

RFI-P server

  • Not a problem if MGX8260 is currently transmitting AIS-P to the remote node

  • Otherwise, check for conditions on MGX8260 that could lead to LOP-P on the remote side

RFI-P connectivity

  • Check for conditions on MGX8260 that could lead to TIM-P or UNEQ-P on the remote side

RFI-P payload

  • Check for conditions on MGX8260 that could lead to PLM-P on the remote side

1Applicable only if ERDI-P is enabled

Respond to other card and line alarms according to the guidelines in the following table:

Symptom Corrective Action

SCC in mismatch state

  • Verify that both SCCs have the identical BIM and back card configuration

OC3 line in major alarm after SCC switch over

  • Verify that the Y-cable set up is correct

  • Prior to using a SCC as a stand by card, verify that all four OC3 lines on that SCC can function properly

SCC fails initialization

  • Use the lsevt command to check for error events logged during initialization and look for a possible OC3 hardware failure

SCC back card type not properly programmed

  • escalate problem to customer support

Clearing Environmental Alarms

The MGX 8260 Media Gateway monitors temperature and voltage at several points in the shelf and on the cards. To view environmental alarms, enter the lsemms command.

The system displays a summary of sensor types, status, and readings. Use the sensor type field described in the following table, find the description that matches your problem, and follow the instructions.

Displayed Information Description

Temperature

The sensor temperature exceeds the maximum threshold value. Try the following possible remedies:

  • Check the fan assembly and verify that all fans are operational.

  • Make sure airflow is not blocked or inhibited.

  • Remove and replace affected cards.

Voltage

The voltage is over or under the threshold value. Try the following possible remedies:

  • Check the front panel PWR circuit LEDs. If PWR A or PWR B is off, check the corresponding fuse.

  • Check the DC power source for proper operation.

  • Check interconnecting power cables and connectors.

Fan speed

A fan has failed or is running too slow. Try the following possible remedies:

  • Check for 6 in. clearance between the top chassis in the rack and other equipment. Remove or move any equipment that is too close.

  • Physically inspect the fan assembly. Remove and replace a fan that is not rotating.


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Posted: Sat Sep 28 14:21:29 PDT 2002
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