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Event ID 21: Remote Desktop Services: Session logon succeeded:

Windows Event ID Lookup: What Windows event IDs mean: 4625, 4624, 4740, 6008, 41, 7045, 1102 and 3,000 more, with Windows' own message text, the fields and what to check.

Look up a Windows event ID from Event Viewer, a SIEM alert or a log export: what it means, the fields it records, and what to check. Many IDs are used by more than one source (event 41 is both a Kernel-Power crash and a boot error), so every definition is shown, the one people usually mean first. The message text is Windows' own, read from the event providers of Windows 10.0.26200.0, 2026-10-28; the notes are ours, based on Microsoft's security auditing reference.

Try: 4625, 4624, 4740, 6008, 41, 1074, 7045, 1102, 4104, 1149

Remote Desktop Services: Session logon succeeded:

Event 21
TerminalServices-LocalSessionManager
TerminalServices-LocalSessionManager/Operational log
Information

Remote Desktop session logon succeeded.

What to check: Source Network Address shows the client; pairs with Security 4624 type 10.

Related: 22, 23, 24, 25, 1149

Message and fields (as Event Viewer shows them) 
Remote Desktop Services: Session logon succeeded:

User: …
Session ID: …
Source Network Address: …

The event logging service encountered a configuration-related error (res=…) for channel

Event 21
Eventlog
Security / System log
Error
Message and fields (as Event Viewer shows them) 
The event logging service encountered a configuration-related error (res=…) for channel …. The error was encountered while processing the … configuration property.

Failed to update leap second data from the registry.

Event 21
Kernel-General
System log
Warning
Message and fields (as Event Viewer shows them) 
Failed to update leap second data from the registry. Reason: …

The OS loader advanced options menu was displayed and the user selected option

Event 21
Kernel-Boot
System log
Information
Message and fields (as Event Viewer shows them) 
The OS loader advanced options menu was displayed and the user selected option ….

Restart Required: To complete the installation of the following updates, the computer must be restarted.

Event 21
WindowsUpdateClient
System log
Information
Message and fields (as Event Viewer shows them) 
Restart Required: To complete the installation of the following updates, the computer must be restarted. Until this computer has been restarted, Windows cannot search for or download new updates: …

The time service is configured to use one or more input providers, however, none of the input providers are available.

Event 21
Time-Service
System log
Error
Message and fields (as Event Viewer shows them) 
The time service is configured to use one or more input providers, however, none of the input providers are available. The time service has no source of accurate time.

HW_INITIALIZATION_DATA data

Event 21
StorPort
System log
Information
Message and fields (as Event Viewer shows them) 
HW_INITIALIZATION_DATA data

WMI Events were bound.

Event 21
WMI-Activity
WMI-Activity/Operational log
Information
Message and fields (as Event Viewer shows them) 
WMI Events were bound. ConsumerType = …; Possiblecause = …

SMB2 Request Set Info

Event 21
SMBServer
SMBServer/Operational log
Information
Message and fields (as Event Viewer shows them) 
SMB2 Request Set Info

A peer was removed from the peer list.

Event 21
Bits-Client
Bits-Client/Operational log
Information
Message and fields (as Event Viewer shows them) 
A peer was removed from the peer list.