Setting up or Updating SNMP via Powershell on a Windows Server 2012 R2

A little while ago, I had to write a Powershell function to update the SNMP settings from a bunch of servers running Windows 2012 R2 Server.

The following cases had to be handled:
 - The SNMP feature could be missing or present
 - The SNMP settings could be existing (Managers / Communities)
 - The SNMP settings could be wiped depending on the servers (Managers / Communities)

So here's what I came up with. Note that we rely on WSMan to make things easier when we're dealing with more than one server and that a new community is always added as Read-Only.

 Function Set-SNMPProperties {
    #requires -version 3
<#
    .SYNOPSIS
            This function will install SNMP if needed and configure the Permitted Managers along with
            the desired communities in read-only via WSMan
    .DESCRIPTION
            This function will install SNMP if needed and configure the Permitted Managers along with
            the desired communities in read-only via WSMan
    .PARAMETER  Computer
            Specifies which computer(s) will be processed
    .PARAMETER  SNMPPermittedManager 
            Specifies which Managers are allowed
    .PARAMETER  SNMPCommunity
            Specifies which Communities are allowed
    .PARAMETER  SNMPClear
            Specifies whether the existing Managers/Communities should be cleared or not
    .EXAMPLE
            Set-SNMPProperties -Computer "lab-fs001.katalykt.lan" `
                -SNMPPermittedManager "lab-centreon001.katalykt.lan" `
                -SNMPCommunity "katalyktRO"
            PSComputerName           SNMPManagers                   SNMPCommunities 
            --------------           ------------                   --------------- 
            lab-fs001.katalykt.lan   lab-centreon001.katalykt.lan   katalyktRO
    .EXAMPLE
            Set-SNMPProperties -Computer "lab-fs001.katalykt.lan", "lab-fs002.katalykt.lan" `
                -SNMPPermittedManager "lab-centreon001.katalykt.lan", "lab-centreon002.katalykt.lan" `
                -SNMPCommunity "katalyktRO", "labRO"
            PSComputerName           SNMPManagers                                         SNMPCommunities 
            --------------           ------------                                         --------------- 
            lab-fs001.katalykt.lan   {lab-centreon001.katalykt.lan, lab-centreon002...}   {katalyktRO, labRO}
            lab-fs002.katalykt.lan   {lab-centreon001.katalykt.lan, lab-centreon002...}   {katalyktRO, labRO}
    .EXAMPLE
            # Assuming the CSV contains one column with the title "Computer"
            Import-Csv -Path D:\Scripts\PSv3\Set-SNMPProperties.csv | ForEach-Object {$_.Computer} | `
                Set-SNMPProperties -SNMPPermittedManager "lab-centreon001.katalykt.lan" `
                    -SNMPCommunity "katalyktRO" `
                    -SNMPClear
            PSComputerName           SNMPManagers                   SNMPCommunities 
            --------------           ------------                   --------------- 
            lab-fs001.katalykt.lan   lab-centreon001.katalykt.lan   katalyktRO
            lab-fs002.katalykt.lan   lab-centreon001.katalykt.lan   katalyktRO
            lab-fs003.katalykt.lan   lab-centreon001.katalykt.lan   katalyktRO
            lab-fs004.katalykt.lan   lab-centreon001.katalykt.lan   katalyktRO
    .NOTES
            NAME:     Set-SNMPProperties
            AUTHOR:   ROULEAU Benjamin
            LASTEDIT: 2016-11-17
    .LINKS
            http://katalykt.blogspot.fr/
#>
    [CmdletBinding()]
    PARAM(
        [Parameter(
            Mandatory,
            ValueFromPipeline,
            ValueFromPipelineByPropertyName)]
        $Computer,
        
        $SNMPPermittedManager,
        $SNMPCommunity,
        [switch]$SNMPClear
    )
    BEGIN {
    }
    PROCESS {
        $Computer | ForEach-Object {
            Try {
                Write-Verbose -Message "[PROCESS - Set-SNMPProperties] Processing computer [$_]"
                If (Test-WSMan -ComputerName $_ -ErrorAction SilentlyContinue) {
                    Invoke-Command -ComputerName $_ -ErrorAction Stop -ErrorVariable ErrInvoke -ScriptBlock {
                        $VerbosePreference = $Using:VerbosePreference
                        
                        # Install the SNMP Service with the WMI provider if needed
                        If ((Get-WindowsFeature -Name "SNMP-Service").Installed -eq "True") {
                            Write-Verbose -Message "[PROCESS - Set-SNMPProperties] The SNMP-Service Windows Feature is already installed"
                        } Else {
                            Write-Verbose -Message "[PROCESS - Set-SNMPProperties] Installing the SNMP-Service Windows Feature"
                            
                            Get-WindowsFeature -Name "SNMP-Service" | Add-WindowsFeature -IncludeAllSubFeature -IncludeManagementTools
                        }
                        # Clear the existing managers/communities if specified
                        If ($SNMPClear) {
                            Write-Verbose -Message "[PROCESS - Set-SNMPProperties] Clearing up the existing Managers and Communities"
                            "PermittedManagers", "ValidCommunities" | ForEach-Object {
                                $Subkey = $_
                                (Get-Item -Path "HKLM:\SYSTEM\CurrentControlSet\Services\SNMP\Parameters\$Subkey").GetValueNames() |  ForEach-Object {
                                    Write-Verbose -Message "[PROCESS - Set-SNMPProperties] Clearing up existing registry record: HKLM:\SYSTEM\CurrentControlSet\Services\SNMP\Parameters\$Subkey\$_"
                                    Remove-ItemProperty -Path "HKLM:\SYSTEM\CurrentControlSet\Services\SNMP\Parameters\$Subkey" -Name $_
                                }
                            }
                        }
                        # Check if the given permitted managers are defined or not
                        Write-Verbose -Message "[PROCESS - Set-SNMPProperties] Checking up Permitted Managers..."
                        $LocalManagers = $using:SNMPPermittedManager
                        If ($LocalManagers) {
                            $PermittedManagers = Get-Item -Path "HKLM:\SYSTEM\CurrentControlSet\Services\SNMP\Parameters\PermittedManagers"
                            $Index = ($PermittedManagers.ValueCount)+1
    
                            $PermittedManagers.GetValueNames() | ForEach-Object {
                                # If this manager is located within the manager array, we remove it from it
                                $Item = (Get-ItemProperty -Path "HKLM:\SYSTEM\CurrentControlSet\Services\SNMP\Parameters\PermittedManagers" -Name $_).$_
                            
                                If ($Item -in $LocalManagers) {
                                    Write-Verbose -Message "[PROCESS - Set-SNMPProperties] Skipping Manager $Item since it's already present"
                                    $LocalManagers = $LocalManagers | Where-Object {$_ -ne $Item}
                                }
                            }
                            # Add the missing managers if needed
                            $LocalManagers | ForEach-Object {
                                Write-Verbose -Message "[PROCESS - Set-SNMPProperties] Adding Manager $_ in the Permitted list with Index $Index"
                                New-ItemProperty -Path "HKLM:\SYSTEM\CurrentControlSet\Services\SNMP\Parameters\PermittedManagers" -Name $Index -Value $_
                                $Index++
                            }
                        }
                        # Check if the community exists, if not we add it
                        Write-Verbose -Message "[PROCESS - Set-SNMPProperties] Checking up the communities..."
                        $using:SNMPCommunity | ForEach-Object {
                            If (-not(Get-ItemProperty -Path "HKLM:\SYSTEM\CurrentControlSet\Services\SNMP\Parameters\ValidCommunities" -Name $_ -ErrorAction SilentlyContinue)) {
                                Write-Verbose -Message "[PROCESS - Set-SNMPProperties] Adding Community $_"
                                New-ItemProperty -Path "HKLM:\SYSTEM\CurrentControlSet\Services\SNMP\Parameters\ValidCommunities" -Name $_ -Value 4 -PropertyType DWORD
                            } Else {
                                Write-Verbose -Message "[PROCESS - Set-SNMPProperties] Skipping Community $_ since it's already present"
                            }
                        }
                        # Return the new SNMP settings for this host
                        New-Object -TypeName PSObject -Property @{
                            SNMPCommunities = (Get-Item -Path "HKLM:\SYSTEM\CurrentControlSet\Services\SNMP\Parameters\ValidCommunities").GetValueNames()
                            SNMPManagers = (Get-Item -Path "HKLM:\SYSTEM\CurrentControlSet\Services\SNMP\Parameters\PermittedManagers").GetValueNames() | ForEach-Object {(Get-ItemProperty -Path "HKLM:\SYSTEM\CurrentControlSet\Services\SNMP\Parameters\PermittedManagers" -Name $_).$_}
                        }
                    }
                } Else {
                    Write-Warning -Message "[PROCESS - Set-SNMPProperties] Computer [$_] could not be contacted via WSMan"
                }
            } Catch {
                If ($ErrInvoke) { Write-Warning -Message ("[PROCESS - Set-SNMPProperties] Invoke-Command failed for computer [{0}] with error {1}" -f $Error[0].OriginInfo, $Error[0].Exception.Message) }
            }
        } | Select PSComputerName, SNMPManagers, SNMPCommunities
    }
    END {
    }
} 

Deploying an High-Availability Domain-Based DFS Namespace with Powershell on Windows Server 2012 R2

As I'm often doing some tests in my lab environment, I try to automate as many things as possible.

So here's a little Powershell script that can be used to deploy an High Availability Domain-Based DFS Namespace on a Windows Server 2012 R2. The UI result can be seen below.

In this lab's case I've been using the following servers to create the root namespace:

• lab-dc001: This is the Windows Server 2012 R2 Domain Controller
• lab-dfs001: This is the first DFS Server
• lab-dfs002: This is the second DFS Server

Both DFS servers are members of my katalykt.lan domain.

Note that the script can be executed on any of our DFS servers and that we rely on PS/CIM sessions to execute some remote commands (i.e Folders creation, SMB Shares)

 # Parameters
$DFS_Root = "lab-dfs001"
$DFS_Secondaries = "lab-dfs002"
$DFS_Domain = "katalykt.lan"
$DFS_Namespace = "root"
$DFS_SmbPath = "E:\DFS\root"
$DFS_Servers = $DFS_Root, $DFS_Secondaries
# Install the DFS Namespace & Replication features
$DFS_Servers | ForEach-Object {Install-WindowsFeature -ComputerName $_ -Name FS-DFS-Namespace,FS-DFS-Replication -IncludeManagementTools}
# Create the Local Folders
$Sessions_DFS = New-PSSession -ComputerName $DFS_Servers
Invoke-Command -Session $Sessions_DFS -Script { New-Item $args[0] –Type Directory } -ArgumentList $DFS_SmbPath
$Sessions_DFS | Remove-PSSession
# Create the Local Shares 
$CIMs_DFS = New-CimSession -ComputerName $DFS_Servers
New-SmbShare –Name $DFS_Namespace –Path $DFS_SmbPath -CimSession $CIMs_DFS
$CIMs_DFS | Remove-CimSession
# Create the main DFS Namespace root
New-DfsnRoot -TargetPath ("\\{0}\{1}" -f $DFS_Root, $DFS_Namespace) -Type DomainV2 -Path ("\\{0}\{1}" -f $DFS_Domain, $DFS_Namespace)
# Add additional targets to our DFS Namespace
$DFS_Secondaries | ForEach-Object {
    New-DfsnRootTarget -Path ("\\{0}\{1}" -f $DFS_Domain, $DFS_Namespace) -TargetPath ("\\{0}\{1}" -f $_, $DFS_Namespace)
}