Event ID 31003: The LmCompatibilityLevel value is different from the default
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The LmCompatibilityLevel value is different from the default.
Event 31003
SMBClient
SMBClient/Connectivity log
Warning
Message and fields (as Event Viewer shows them)
The LmCompatibilityLevel value is different from the default.
Configured LM Compatibility Level: …
Default LM Compatibility Level: 3
Guidance:
LAN Manager (LM) authentication is the protocol used to authenticate Windows clients for network operations. This includes joining a domain, accessing network resources, and authenticating users or computers. This determines which challenge/response authentication protocol is negotiated between the client and the server computers. Specifically, the LM authentication level determines which authentication protocols the client will try to negotiate or the server will accept. The value set for LmCompatibilityLevel determines which challenge/response authentication protocol is used for network logons. This value affects the level of authentication protocol that clients use, the level of session security negotiated, and the level of authentication accepted by servers.
Value (Setting) - Description
0 (Send LM & NTLM responses) - Clients use LM and NTLM authentication and never use NTLMv2 session security. Domain controllers accept LM, NTLM, and NTLMv2 authentication.
1 (Send LM & NTLM - use NTLMv2 session security if negotiated) - Clients use LM and NTLM authentication, and use NTLMv2 session security if the server supports it. Domain controllers accept LM, NTLM, and NTLMv2 authentication.
2 (Send NTLM response only) - Clients use NTLM authentication only and use NTLMv2 session security if the server supports it. Domain controllers accept LM, NTLM, and NTLMv2 authentication.
3 (Send NTLM v2 response only) - Clients use NTLMv2 authentication only and use NTLMv2 session security if the server supports it. Domain controllers accept LM, NTLM, and NTLMv2 authentication.
4 (Send NTLMv2 response only/refuse LM) - Clients use NTLMv2 authentication only and use NTLMv2 session security if the server supports it. Domain controllers refuse LM and accept only NTLM and NTLMv2 authentication.
5 (Send NTLM v2 response only/refuse LM & NTLM) - Clients use NTLMv2 authentication only and use NTLMv2 session security if the server supports it. Domain controllers refuse LM and NTLM and accept only NTLMv2 authentication.
Incompatibly configured LmCompatibility levels between a client and server (such as 0 on a client and 5 on a server) prevent access to the server. Non-Microsoft clients and servers also provide these configuration settings.