Querying SNMP Devices

PowerShell Networking
1

There are a few different ways to query SNMP on devices. I will share 3 ways that I have found to be pretty accurate and quick.

Before we begin here are 3 utilities you will need to perform the queries.
1 utility is an executable the other 2 are DLL files that you will be loading into your powershell session.

SNMPGet.exe Tool

The latest release of “SharpSnmpLib.dll” can be downloaded from:

The latest release of “SnmpSharpNet.dll” can be downloaded from:

===========================================

Using SNMPGet.exe

CLS

#Path to SNMPGet.exe
$SNMPGet = "C:\Users\James\Desktop\SNMP\SnmpGet.exe"

$CommunityString = "public"
$OID = ".1.3.6.1.2.1.1.1.0"
$IP = "123.123.123.123"

Try
{
	if(($(& $SNMPGet -r:$IP -c:$CommunityString -o:$OID -t:1) | Select-Object -Skip 3)  -notlike "*Failed*")
	{
		$True
	}
}
Catch
{}

Using SnmpSharpNet.dll

CLS

#Path to SnmpSharpNet.dll
$DLL = "C:\Users\James\Desktop\SNMP\8-5\SnmpSharpNet.dll"
Add-Type -Path $DLL

$CommunityString = "public"
$OID = ".1.3.6.1.2.1.1.1.0"
$IP = "123.123.123.123"

$SNMP = new-object SnmpSharpNet.SimpleSnmp($IP,$CommunityString)
$SNMP.Timeout = 100
$Version = "Ver1"
		
Try
{
	if($NULL -ne ($SNMP.Get([SnmpSharpNet.SnmpVersion]::$Version,$OID)).Values)
	{
		$True
	}
}
Catch
{}

Using SharpSnmpLib.dll

CLS

#Path to SnmpSharpNet.dll
$DLL = "C:\Users\James\Desktop\SNMP\8-5\SharpSnmpLib.dll"
Add-Type -Path $DLL

function Get-SnmpData 
{
    [CmdletBinding()]
    param (
        # Endpoint IP address.
        [Parameter(
            Mandatory = $true,
            HelpMessage = 'Endpoint IP address'
        )]
        [Net.IPAddress]$IP,

        # OID list.
        [Parameter(
            Mandatory = $true,
            HelpMessage = 'OID list'
        )]
        [string[]]$OID,
    
        # SNMP Community.
        [string]$Community = 'public', 
    
        # SNMP port.
        [int]$UDPport = 161,

        # SNMP version.
        [Lextm.SharpSnmpLib.VersionCode]$Version = 'V2',

        # Time out value.
        [int]$TimeOut = 3000
    )

    $variableList = New-Object Collections.Generic.List[Lextm.SharpSnmpLib.Variable]

    foreach ($singleOID in $OID) 
    {
        $variableList.Add($(
            New-Object Lextm.SharpSnmpLib.ObjectIdentifier $singleOID
        ))
    }
 
    $endpoint = New-Object Net.IpEndPoint $IP, $UDPport
 
    try 
    {
        $message = [Lextm.SharpSnmpLib.Messaging.Messenger]::Get(
            $Version, 
            $endpoint, 
            $Community, 
            $variableList, 
            $TimeOut
        )
    } catch 
    {
        Write-Warning "SNMP Get error: $_"
        return
    }
 
    foreach ($variable in $message) 
    {
        New-Object PSObject -Property @{
            OID = $variable.Id.ToString()
            Data = $variable.Data.ToString()
        }
    }
}

$CommunityString = "public"
$OID = ".1.3.6.1.2.1.1.1.0"
$IP = "123.123.123.123"

$SNMP = new-object SnmpSharpNet.SimpleSnmp($IP,$CommunityString)
$SNMP.Timeout = 100
$Version = "Ver1"
		
Try
{
	if($NULL -ne ((Get-SnmpData -IP $IP -Community $CommunityString -Version V1 -TimeOut 100 -OID $OID -WarningAction SilentlyContinue).Data))
	{
		$True
	}
}
Catch
{}

In terms of Performance if you’re running this against multiple devices the speed is fastest with the script utilizing “SnmpSharpNet.dll”.