Windows Native Extension Agent DLLs

Windows Native Extension Agent DLLs

The true power of SNMP Service Windows based monitoring comes from the use of SNMP extension Agent DLLs. There are numerous extension DLLs provided by Microsoft with the Windows products. There are also many third party extension DLLs provided by vendors of Windows applications.

When it comes to Windows native extension DLLs the initial post-installation make-up depends on the NuDesign’s Service “first install” scenario. There are two “first install” scenarios for NuDesign’s secure SNMPv3 Master Agent Service for Windows:

  1. install after Windows’ native SNMPv1/v2c Agent Service has already been installed and enabled
  2. install on Windows with no previous native SNMPv1/v2c Agent Service installation

In scenario 1.) NuDesign’s Service will disable the Microsoft’s native Service, while copying over to its own configuration registry, the Microsoft Service based configuration. Typically, the folowing Microsoft extension DLLs will be installed (64bit system example):

Extension Agent Name DLL MIB
LAN Manager MIB2 Agent *\lmmib2.dll lmmib2.mib
HostMIB *\hostmib.dll rfc2790.mib or hostmib.mib
RFC1156 Agent *\inetmib1.dll rfc1156-mib.mib
SNMPMIB *\snmpmib.dll note 1
SNMP_EVENTS *\evntagnt.dll note 2
Wow64 Proxy Agent *\wow64mib.dll note 3


  • DLL path *\ is c:\Windows\System32\
  • note 1 – this MIB is loaded but its implementation is superseded by Service’s internal v3 implementation
  • note 2 – evntagnt.dll performs mapping of user selected Windows events to SNMP traps as per configuration done using Windows utilities: evntwin.exe & evntcmd.exe (read more)
  • note 3 – a proxy agent, not a MIB, used in 64bit systems to provide 32bit DLL’s visibility (read more)

A number of additional Microsoft DLLs may be installed, depending on the type of services pre-installed with the Windows OS, for example: httpmib.dll, if IIS has been installed since IIS provides its own MS SNMP based configuration.

In scenario 2.) NuDesign’s Service will install its own default SNMPv3 configuration, including SNMPv3 defaults (please review Service’s Help file for more information) and will typically add the lmmib2.dll, hostmib.dll and inetmib.dll Microsoft extension DLLs found in your Windows’ WinSxS depository.

Running NuDesign’s SNMPv3 Configuration Editor at this point provides for optional additions / deletions of Microsofts’ native and / or 3rd party extension DLLs.

Developing Custom Extension Agent DLLs

For custom monitoring applications NuDesign provides the SNMP Agent Studio for Windows, a code generation tool used in automatic generation of Extension Agent DLLs for any custom, application-specific MIB module. The tool greatly simplifies development of Extension DLLs. It is as simple as reading a MIB module into the wizards, it produces complete project files and the source code that needs to be instrumented for each read / write object. The notifications are auto-handled as well.

Annual Support Contracts and Upgrades

The Annual Technical Support and Subscription Service Contract provides one year of product enhancement and maintenance updates plus access to our engineering team (please review the terms here).  For more details please see our Purchase SNMPv3 Service page.