Azure AD Connect Sync Stopped Password Sync when set LAN Manager authentication level 5

Joseph Lamb 21 Reputation points
2021-10-05T14:46:22.507+00:00

Azure AD Connect Sync Stopped Password Sync when set LAN Manager authentication level 5 (Send NTLMv2 response only. Refuse LM & NTLM). Is there something I can do to allow AD sync to send NTLMv2 responses?

Microsoft Entra ID
Microsoft Entra ID
A Microsoft Entra identity service that provides identity management and access control capabilities. Replaces Azure Active Directory.
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  1. Clément BETACORNE 2,031 Reputation points
    2021-10-06T08:24:43.567+00:00

    Ok so I think you should align your configuration between your domain controllers and your Azure AD Connect.
    You should configure the GPO for your domain controllers to at least 3 (Send NTLMv2 response only) if you don't have application which require less and configure your Azure AD Connect with 5 (Send NTLMv2 response only. Refuse LM & NTLM).

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  1. Clément BETACORNE 2,031 Reputation points
    2021-10-05T17:43:13.877+00:00

    Hello,

    I have an Azure AD connect with the Lmcompatibilitylevel 5 and I have no issue with it.
    Is it possible to give us the version of Azure AD Connect : 

    (Get-ADSyncGlobalSettings).Parameters | select Name,Value

    Check the : Microsoft.Synchronize.ServerConfigurationVersion

    Check also the configuration of your domain controllers regarding LAN Manager authentication level, which level they have ?

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  2. Joseph Lamb 21 Reputation points
    2021-10-05T17:51:13.31+00:00

    Thank you for responding:

    Microsoft.Synchronize.ServerConfigurationVersion 1.6.4.0

    Domain controllers are at
    Send LM & NTLM responses 0

    This morning I changed a Domain Controllers GPO to Lmcompatibilitylevel 5 and ADsync stopped working. So I reverted it back.

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  3. Joseph Lamb 21 Reputation points
    2021-10-06T14:09:33.867+00:00

    I changed LAN Authentication to Level 3 and no problems.

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