Hi Samba team, Could someone point me to a documentation which describes which NTLM flag combination in type 1 & 2 create which type 3 response. As far as I read MS has the following client/DC configuration combinations. Send LM & NTLM responses Clients use LM and NTLM authentication, and never use NTLMv2 session security; DCs accept LM, NTLM, and NTLMv2 authentication. Send LM & NTLM - use NTLMv2 session security if negotiated Clients use LM and NTLM authentication, and use NTLMv2 session security if server supports it; DCs accept LM, NTLM, and NTLMv2 authentication. Send NTLM response only Clients use NTLM authentication only, and use NTLMv2 session security if server supports it; DCs accept LM, NTLM, and NTLMv2 authentication. Send NTLMv2 response only Clients use NTLMv2 authentication only, and use NTLMv2 session security if server supports it; DCs accept LM, NTLM, and NTLMv2 authentication. Send NTLMv2 response only\refuse LM Clients use NTLMv2 authentication only, and use NTLMv2 session security if server supports it; DCs refuse LM (accept only NTLM and NTLMv2 authentication). Send NTLMv2 response only\refuse LM & NTLM Clients use NTLMv2 authentication only, and use NTLMv2 session security if server supports it; DCs refuse LM and NTLM (accept only NTLMv2 authentication). but I can’t find a clear relation to the flags used during the NTLM type 1 & 2 exchange e.g. which of the flags need to be set in type 2 in particular to determine the response in type 3. e.g. does DCs refuse LM (accept only NTLM and NTLMv2 authentication). mean Negotiate Lan Manager Key = 0, Negotiate NTLM key = 1 and Negotiate Extended Security = 1 Negotiate 56 Negotiate Key Exchange Negotiate 128 Negotiate 0x10000000 Negotiate 0x08000000 Negotiate 0x04000000 Negotiate Version Negotiate 0x01000000 Negotiate Target Info Request Non-NT Session Negotiate 0x00200000 Negotiate Identify Negotiate Extended Security Target Type Share Target Type Server Target Type Domain Negotiate Always Sign Negotiate 0x00004000 Negotiate OEM Workstation Supplied Negotiate OEM Domain Supplied Negotiate Anonymous Negotiate NT Only Negotiate NTLM key Negotiate 0x00000100 Negotiate Lan Manager Key Negotiate Datagram Negotiate Seal Negotiate Sign Request 0x00000008 Request Target Negotiate OEM Negotiate UNICODE Thank you Markus