The Windows Member Server GPO security templates (included with the Windows Server 2003 Security Guide) enable minimum session security for NTLM security support provider (SSP)-based servers and clients. Specifically, the Windows Enterprise Client Member Server GPO template configures the following NTLM settings:
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Message integrity (encryption)
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Message confidentiality
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NTLMv2 authentication
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128-bit encryption
NTLMv2 authentication does not operate correctly on the RTM version of Windows Server 2003 clusters. Specifically, on a Windows Server 2003 cluster, enabling NTLMv2 authentication for NTLM SSP prevents the Cluster service from starting. However, NTLM version 1 session security with message integrity, message confidentiality, and 128-bit encryption is functional. Therefore, the Windows Enterprise Client Member Server GPO security template causes Exchange cluster nodes to fail because the GPO security templates enforce NTLMv2 authentication.
To enable Exchange 2003 clustering where the Windows Member Server GPO security templates are being enforced, you must install the Windows hotfix described in the Microsoft Knowledge Base article 890761, "You receive an "Error 0x8007042b" error message when you add or join a node to a cluster if you use NTLM version 2 in Windows Server 2003."
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To allow NTLMv2 Session Security to operate correctly, it is recommended that you install the hotfix. If NTLMv2 authentication is enabled and this hotfix is not applied, the Windows Clustering service will not start.
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Again, it is important to stress that applying the Exchange 2003 Cluster Node Base GPO template in isolation does not harden your Exchange environment. The Exchange 2003 Cluster Node Base GPO template assumes that both the Exchange Backend and the Windows Server 2003 Enterprise Client Member Server Security GPO security templates have been applied and are inherited by the OU where you placed your Exchange cluster nodes.