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AR Router Troubleshooting Guide

This Product Documentation provides guidance for maintaining AR Enterprise Router, covering common information collection and fault diagnostic commands, typical fault troubleshooting guide, and troubleshooting.
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Link Failed to Be Established on ISDN Interfaces

Link Failed to Be Established on ISDN Interfaces

Common Causes

This fault is commonly caused by one of the following:
  • The physical interface cannot go Up.
  • The cable between ISDN interfaces is faulty.
  • The interface configuration is incorrect.
  • Packets are incorrectly sent.
  • The network-side device is faulty.

Troubleshooting Flowchart

Figure 17-8 shows the troubleshooting flowchart.
Figure 17-8  Link failing to be established on ISDN interfaces

Troubleshooting Procedure

NOTE:

Saving the results of each troubleshooting step is recommended. If troubleshooting fails to correct the fault, you will have a record of your actions to provide Huawei technical support personnel.

Procedure

  1. Check that the physical status of the interface is Up.

    Run the display controller e1 command in the system view to check whether the physical status of the interface is Up. The following information uses the display on E1 1/0/0 as an example.

    • If "E1 1/0/0 current state : Administratively DOWN" is displayed, E1 1/0/0 has been shut down by the administrator. Run the undo shutdown command on E1 1/0/0 to enable it. If "E1 1/0/0 current state : DOWN" is displayed after the undo shutdown command is run, rectify the fault according to the following table.

    • If "E1 1/0/0 current state : DOWN" is displayed, check the following items.

      Item

      Description

      Follow-up Operation

      Check that the connection and cable between the local and remote interfaces and modules on interfaces are working properly.

      If the Alarm State field is displayed as Loss-of-Signal, the following faults may occur:
      1. The local and remote interfaces are not properly connected.
      2. The interface modules fail.
      3. The cable between the two interfaces is disconnected.

      Connect the two interfaces properly. If the fault persists, replace the cable or interface board.

      Check the working mode of the local and remote interfaces. The Work Mode field indicates the working mode of an interface:
      • E1 FRAMED: The interface works in framed mode.
      • E1 UNFRAMED: The interface works in unframed mode.
      The local and remote interfaces must work in framed mode.
      If the local and remote interfaces work in unframed mode, run the pri-set command on the CE1 interface view to set the working mode to framed mode.
      Check whether the local and remote interfaces use the same frame format. The Frame-format field indicates the frame format of an interface:
      • CRC4: The frame is a multi-frame.
      • NO-CRC4: The frame is a basic frame, which is also called a dual-frame or an odd-even frame.
      The local and remote interfaces must use the same frame format.
      If the local and remote interfaces use different frame formats, run the frame-format command in the CE1 interface view to reconfigure the frame format so that the two interfaces use the same frame format.
      Check whether the local and remote interfaces use the same encoding and decoding mode. The Line Code field indicates the encoding and decoding mode of an interface. The value is HDB3.

      The local and remote interfaces must use the same encoding and decoding mode.

      If the remote interface does not use the HDB3 mode, change it to the HDB3 mode so that the local and remote interfaces use the same mode.
      Check whether the clock mode is correctly configured for the local and remote interfaces. When two routers are directly connected using two CE1 interfaces, the two CE1 interfaces work in master clock mode and slave clock mode respectively. If the clock mode is incorrectly configured for the local and remote interfaces, run the clock command in the CE1 interface view to correctly configure the clock mode.
      Check whether the loopback function is configured on the local and remote interfaces.

      Run the display this command in the CE1 interface view to check whether the loopback function is configured on the interface. If loopback local, loopback payload, or loopback remote is displayed, the loopback function is configured on the interface. The loopback function will cause the interface to alternate between Up and Down states. Therefore, disable the loopback function after loopback detection is complete.

      NOTE:

      After the display controller e1 command is run in the system view, if the Alarm State field is displayed as Alarm-Indication-Signal, the loopback function may be configured on the interface.

      If the loopback function has been configured on the local and remote interfaces, run the undo loopback command in the CE1 interface view to disable the loopback function.

      If "E1 1/0/0 current state : DOWN" is still displayed, go to step 4.

    • If "E1 1/0/0 current state : UP" is displayed, E1 1/0/0 is in Up state. Go to step 2.

  2. Check that packets are sent and received on the local and remote interfaces.

    NOTE:

    After the display controller e1 command is run in the system view, if the Alarm State field is displayed as Remote-Alarm-Indication, packets may be incorrectly sent or received on the local and remote interfaces.

    Run the debugging isdn q921, terminal debugging, and terminal monitor commands in sequence to check sent packets. In the command output, U->N indicates a direction from the user-side interface to the network-side interface, and Len indicates the SABME frame length. The correct SABME frame length is 3 bytes and the contents of a SABME frame is 00 01 7F or 02 01 7F.

    • If the following information is displayed, the length and contents of the sent SABME frames are incorrect. Restart or replace the device.
      <Huawei>
      Oct 12 2007 11:54:42.240.1+08:00 Huawei Q921/7/Q921_Debug: Serial1/0/0:15                                                           
          U->N Len=7 00 01 7F  00 00 00 00 
          U->N sapi=00 tei=00 c/r=0  SABME  p=1   
      
      <Huawei>
      Oct 12 2007 11:54:43.240.1+08:00 Huawei Q921/7/Q921_Debug: Serial1/0/0:15                                                           
          U->N Len=7 00 01 7F 00 00 00 00                                                                                                   
          U->N sapi=00 tei=00 c/r=0  SABME  p=1  
      
      <Huawei>
      Oct 12 2007 11:54:44.240.1+08:00 Huawei Q921/7/Q921_Debug: Serial1/0/0:15                                                           
          U->N Len=7 00 01 7F 00 00 00 00                                                                                                   
          U->N sapi=00 tei=00 c/r=0  SABME  p=1  
      
    • If the following information is displayed, SABME frames are correctly sent. Go to step 3.
      <Huawei>
      Oct 12 2007 11:54:42.240.1+08:00 Huawei Q921/7/Q921_Debug: Serial1/0/0:15                                                           
          U->N Len=3 00 01 7F                                                                                                             
          U->N sapi=00 tei=00 c/r=0  SABME  p=1  
      
      <Huawei>
      Oct 12 2007 11:54:43.240.1+08:00 Huawei Q921/7/Q921_Debug: Serial1/0/0:15                                                           
          U->N Len=3 00 01 7F                                                                                                             
          U->N sapi=00 tei=00 c/r=0  SABME  p=1  
      
      <Huawei>
      Oct 12 2007 11:54:44.240.1+08:00 Huawei Q921/7/Q921_Debug: Serial1/0/0:15                                                           
          U->N Len=3 00 01 7F                                                                                                             
          U->N sapi=00 tei=00 c/r=0  SABME  p=1
      
  3. Check that the network-side interface sends response packets.

    NOTE:

    After the display controller e1 command is run in the system view, if the Alarm State field is displayed as Remote-Alarm-Indication, packets may be incorrectly sent or received on the local and remote interfaces; if the Alarm State field is displayed as Loss-of-Frame, an error occurs when packets are sent on the remote interface.

    Run the debugging isdn q921, terminal debugging, and terminal monitor commands in sequence to check sent packets. In the command output, N->U indicates a direction from the network-side interface to the user-side interface. If response packets have been received from the remote end, information is displayed following N->U.

    • If the following information (only U->N information) is displayed, no response packet is sent from the network-side interface. Check whether the network-side device is faulty.
      <Huawei>
      Oct 12 2007 14:28:51.430.1+08:00 Huawei Q921/7/Q921_Debug: Serial1/0/0:15                                                           
          U->N Len=3 00 01 7F                                                                                                        
          U->N sapi=00 tei=00 c/r=0  SABME  p=1    
      
      <Huawei>
      Oct 12 2007 14:28:52.430.1+08:00 Huawei Q921/7/Q921_Debug:                                                                          
       [FUN: ISDN_Q921_T200Out, LINE: 2182] ISDN Layer 2 link state change -> TEI_ASSIGNED    
      
      <Huawei>
      Oct 12 2007 14:28:57.430.1+08:00 Huawei Q921/7/Q921_Debug: Serial1/0/0:15                                                           
          U->N Len=3 00 01 7F                                                                                                        
          U->N sapi=00 tei=00 c/r=0  SABME  p=1       
      
      <Huawei>
      Oct 12 2007 14:28:57.430.2+08:00 Huawei Q921/7/Q921_Debug:                                                                          
       [FUN: ISDN_Q921_HandleEstablishReq, LINE: 185] ISDN Layer 2 link state change -> AWAITING_ESTABLISHMENT  
      
      <Huawei>
      Oct 12 2007 14:29:00.430.1+08:00 Huawei Q921/7/Q921_Debug: Serial1/0/0:15                                                           
          U->N Len=3 00 01 7F                                                                                                        
          U->N sapi=00 tei=00 c/r=0  SABME  p=1                                                                                      
      Q921/7/Q921_Debug:                                                                          
       [FUN: ISDN_Q921_T200Out, LINE: 2182] ISDN Layer 2 link state change -> TEI_ASSIGNED     
      
    • If the following information (both U->N and N->U information) is displayed, the network-side interface correctly sends response packets. Go to step 4.
      <Huawei>
      Oct 12 2007 14:28:57.430.1+08:00 Huawei Q921/7/Q921_Debug: Serial1/0/0:15                                                           
          U->N Len=3 00 01 7F                                                                                                             
          U->N sapi=00 tei=00 c/r=0  SABME  p=1  
      
      <Huawei>
      Oct 12 2007 14:28:57.430.1+08:00 Huawei Q921/7/Q921_Debug: Serial1/0/0:15                                                           
          U->N Len=3 00 01 7F                                                                                                             
          U->N sapi=00 tei=00 c/r=0  SABME  p=1 
      
      <Huawei>
      Oct 12 2007 14:28:57.430.1+08:00 Huawei Q921/7/Q921_Debug: Serial1/0/0:15                                                           
          U->N Len=3 00 01 7F                                                                                                             
          U->N sapi=00 tei=00 c/r=0  SABME  p=1  
      
      <Huawei>
      Oct 12 2007 13:55:20.680.2+08:00 Huawei Q921/7/Q921_Debug: Serial1/0/0:15                                                           
          N->U Len=3 02 01 73                                                                                                        
          N->U sapi=00 tei=00 c/r=1  UA  f=1                               
      
      <Huawei>
      Oct 12 2007 13:55:20.680.3+08:00 Huawei Q921/7/Q921_Debug:                                                                          
       [FUN: ISDN_Q921_HandleOnTEIAssign, LINE: 1054] ISDN Layer 2 link state change -> MULTIPLE_FRAME_ESTABLISHED  
      
  4. Collect the following information and contact technical support personnel.
    • Results of the preceding troubleshooting procedure

    • Configuration files, log files, and alarm files of the device

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Updated: 2019-05-10

Document ID: EDOC1000079719

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