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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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An AR Cannot Establish an L2TP Tunnel

An AR Cannot Establish an L2TP Tunnel

This section provides a troubleshooting case for the fault that an AR cannot establish an L2TP tunnel.


Figure 25-28  Establishing an L2TP tunnel between a remote dialup user and the headquarters based on the authentication domain

LNS configurations:

 l2tp enable                               
acl number 2001                         
 rule 5 permit source
ip pool lns                             
 network mask
 authentication-scheme lmt                                                      
  authentication-scheme lmt
 local-user password cipher %^%#_<`.CO&(:LeS/$#F\H0Qv8B]KAZja3}3q'RNx;VI%^%#
 local-user privilege level 0  
 local-user service-type ppp
interface GigabitEthernet1/0/0.1
 dot1q termination vid 217
 ip binding vpn-instance internet
 ip address
 nat outbound 2999                       
interface Virtual-Template1              
 ppp authentication-mode chap domain   
 remote address pool lns
 ppp ipcp dns                
 ip address
l2tp-group 1                           
 undo tunnel authentication           
 allow l2tp virtual-template 1

Fault Description

An AR cannot establish an L2TP tunnel.

Fault Analysis

  1. On the LNS, run the debugging l2tp all command.
    <Huawei> terminal monitor
    <Huawei> terminal debugging
    <Huawei> debugging l2tp all
    <Huawei> debugging ppp all
    Jan 30 2018 18:43:14.110.1+00:00 Huawei L2TP/7/L2TDBG:
      Recv SCCRQ:
          Tunnel:1,  state:1
    Jan 30 2018 18:43:14.110.2+00:00 Huawei L2TP/7/L2TDBG:
    L2tp CONTRL:  Check SCCRQ MSG Type 1
    Jan 30 2018 18:43:14.110.3+00:00 Huawei L2TP/7/L2TDBG:
     L2tp ERROR: Invalid Requested Host.

    The information collected from the device indicates that the incorrect L2TP configuration is caused by an invalid requested host.

  2. The analysis indicates that the interface of the destination device is configured with an IP address and is bound to a VPN instance, but the VPN instance of the source device initiating the L2TP tunnel establishment request is not specified. You need to run the allow l2tp command in the L2TP group view to configure the LNS to receive the L2TP tunnel establishment requests initiated by the device PC1 that belongs to the VPN instance internet and to use the virtual interface template virtual-template 1. Then, the fault is rectified.


Configure the LNS to receive L2TP tunnel establishment requests initiated by the device PC1 that belongs to the VPN instance internet and to use the virtual interface template virtual-template 1.

<Huawei> system-view  
[Huawei] l2tp-group 1  
[Huawei-l2tp1] allow l2tp virtual-template 1 remote PC1 vpn-instance internet

Conclusions and Suggestions

If interfaces used by an L2TP tunnel are bound to VPN instances, the VPN instance of the device initiating an L2TP tunnel establishment request needs to be specified so that the request can be received by the destination device.

Updated: 2019-05-10

Document ID: EDOC1000079719

Views: 453879

Downloads: 4311

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