L2TP failed to use AD authentication with CHAP

The Solution for this case is mainly by changing the authentication protocol on windows VPN connection setting by choosing properties of VPN connection à Security à Authentication à select only PAP protocol.

The second part of the solution is to check the Virtual-Template configuration, and in this case we should have PAP authentication enable and set in the ppp authentication (which is by default), so you can remove CHAP protocol or you can keep it, it doesn’t matter as long as windows configured to use PAP only and PAP is configured in the virtual interface.

interface Virtual-Template 0

  ppp authentication-mode pap   or ppp authentication-mode pap chap

 remote service-scheme
 l2tpSScheme_1493323626170  ip address 192.168.20.1 255.255.255.0

 undo service-manage enable

Consider protocol matching for any configuration.

For more details : https://support.huawei.com/enterprise/en/knowledge/EKB1000860748

Thanks