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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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The User Fails to Log in to the Server Through Telnet

The User Fails to Log in to the Server Through Telnet

Common Causes

This fault is commonly caused by one of the following:

  • The route is unreachable, and the user cannot set up a TCP connection with the server.
  • The number of users logging in to the server reaches the upper threshold.
  • An ACL is configured in the VTY user interface view.
  • The access protocol specified in the VTY user interface view is incorrect. For example, when the access protocol is configured to SSH through the protocol inbound ssh command, the user cannot log in to the server through Telnet.

Troubleshooting Flowchart

Figure 13-2 shows the troubleshooting flowchart.

Figure 13-2  Troubleshooting flowchart for the fault that the client fails to log in to the server through Telnet

Troubleshooting Procedure

Context

NOTE:

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

Procedure

  1. Check whether the Telnet client can ping through the server.

    Run the ping command to check the network connectivity. If the ping fails, the Telnet connection cannot be established between the user and server.

    If the ping fails, see The Ping Operation Fails to locate the problem so that the Telnet client can ping through the server.

  2. Check whether the number of users logging in to the server reaches the upper threshold.

    Log in to the server through a console interface and then run the display users command to check whether all the current VTY channels are in use. By default, a maximum of 5 users can log in to the server through VTY channels. Run the display user-interface maximum-vty command to view the allowed maximum number of login users.

    <Huawei> display user-interface maximum-vty
     Maximum of VTY user:5
    <Huawei> display users
      User-Intf    Delay    Type   Network Address     AuthenStatus    AuthorcmdFlag      
    + 0   CON 0   00:00:00                                   pass           no     
      Username : Unspecified             
    
      129 VTY 0   00:52:27  TEL    192.168.1.100             pass        
      Username : Unspecified                                             
                                                                      
      132 VTY 1   00:43:22  TEL    192.168.1.101              pass       
      Username : Unspecified                                             
                                                                         
      133 VTY 2   00:14:54  TEL    192.168.1.102             pass       
      Username : Unspecified                                          
                                                                    
      135 VTY 3   00:00:00  TEL    192.168.1.103              pass       
      Username : Unspecified              
    
      135 VTY 4   00:00:00  TEL    192.168.1.104              pass       
      Username : Unspecified

    If the number of users logging in to the server reaches the upper threshold, you can run the user-interface maximum-vty vty-number command to increase the maximum number of users allowed to log in to the server through VTY channels to 15.

    <Huawei> system-view
    [Huawei] user-interface maximum-vty 15

  3. Check that an ACL is configured in the VTY user interface view.

    [Huawei] user-interface vty 0 4
    [Huawei-ui-vty0-4] display this
    user-interface vty 0 4
     acl 2000 inbound
     authentication-mode password
     user privilege level 3
     idle-timeout 0 0
    

    If an ACL is configured but the IP address of the client to be permitted is not specified in the ACL, the user cannot log in to the server through Telnet. To enable a user with a specific IP address to log in to the server through Telnet, permit the IP address of the user in the ACL.

  4. Check that the access protocol configured in the VTY user interface view is correct.

    [Huawei] user-interface vty 0 4
    [Huawei-ui-vty0-4] display this
    user-interface vty 0 4
     authentication-mode password
     user privilege level 3
     idle-timeout 0 0
     protocol inbound ssh
    Run the protocol inbound { all | ssh | telnet } command to configure the user access protocol. By default, the user access protocol is Telnet.
    • If the user access protocol is SSH, the user cannot log in to the server through Telnet.
    • If the user access protocol is "all", the user can log in to the server through Telnet or SSH.

  5. Check that the authentication mode is configured in the user interface view.

    • If you run the authentication-mode password command to configure the authentication mode for the user logging in to the server through the VTY channel to password, run the set authentication password command to set the authentication password.

    • If you run the authentication-mode aaa command to configure the authentication mode to aaa, you should run the local-user command to add a local user.

  6. If the fault persists, collect the following information and contact technical support personnel:

    • Results of the preceding troubleshooting procedures
    • Configuration files, log files, and alarm files of the devices

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Updated: 2019-05-10

Document ID: EDOC1000079719

Views: 452059

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