dhcp.ps1 - powershell script by ActiveXperts Software

dhcp.ps1 checks for maximum number of IP addresses in use.

Use dhcp.ps1 directly from ActiveXperts Network Monitor; in the Manager's 'Monitor' menu, select 'New Check (Script)' and select dhcp.ps1. Configure the required parameter, or press 'Load a working sample'.

In ActiveXperts Network Monitor, Administrators can use three different scripting languages: Powershell, VBScript and SSH.

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dhcp.ps1 script code

#################################################################################
# ActiveXperts Network Monitor PowerShell script.
# For more information about ActiveXperts Network Monitor, visit the ActiveXperts 
# Network Monitor web site at http://www.activexperts.com
#################################################################################
# Script
#     Dhcp.ps1
# Description: 
#     Check for maximum number of IP addresses in use.
#     Requires SNMP running on the DHCP server and monitoring system.
#     This function uses ActiveXperts Network Component.
#     ActiveXperts Network Component is automatically licensed when ActiveXperts Network Monitor is purchased
#     For more information about ActiveXperts Network Component, see: www.activexperts.com/network-component
# Declare Parameters:
#     1) strDhcpServer (string) - Host name or IP address of the DHCP server
#     2) strSubnet (string) - Subnet.
#     3) numMaxAllowed (int) - maxmimum number of IP addresses allows
# Usage:
#     .\Dhcp.ps1 '<Hostname | IP>' 'x.x.x.x' <Maximum Value>
# Sample:
#     .\Dhcp.ps1 'localhost' '192.168.31.0' 200
#################################################################################

# -- Declare Parameters
param( [string]$strHost = '', [string]$strSubnet = '', [int]$nMaxAllowed = -1 )

# -- Use _activexperts.ps1 with common functions
. 'C:\Program Files\ActiveXperts\Network Monitor\Scripts\Monitor (ps1)\_activexperts.ps1'


#################################################################################
# // --- Private Functions section ---
#################################################################################

function checkDhcpMaxInuse( $strHost, $strOID, $nMaxAllowed, [ref]$strData, [ref]$strExplanation )
{
  $strCommunity = 'public'

  # Create instance of SNMP object
  $objSnmpManager = new-object -comobject AxNetwork.SnmpManager
  $objConstants = new-object -comobject AxNetwork.NwConstants

  # Initialize SNMP object
  $objSnmpManager.LogFile = 'c:\temp\_log.log'
  $objSnmpManager.ProtocolVersion = $objConstants.nwSNMP_VERSION_V2C
  $objSnmpManager.Initialize()
  
  if( $objSnmpManager.LastError -ne 0 )
  {
    $strExplanation.value = 'ERROR: Unable to initialize ActiveXperts Network Component SNMP object'
    return $AXERROR
  }

  # Open connection to (remote) SNMP agent
  $objSnmpManager.Open( $strHost, $strCommunity )
  
  if( $objSnmpManager.LastError -ne 0 )
  {
    $strExplanation.value = 'ERROR: Unable to connect to agent [' + $strHost + '], community [' + $strCommunity + '], error #' + $objSnmpManager.LastError + ': ' + $objSnmpManager.GetErrorDescription( $objSnmpManager.LastError )
    return $AXERROR
  }

  $objSnmpObject = $objSnmpManager.Get( $strOID )

  if( $objSnmpManager.LastError -ne 0 )
  {
    $strExplanation.value = 'UNCERTAIN: Unable to retrieve [' + $strOID + ', error #' + $objSnmpManager.LastError + ': ' + $objSnmpManager.GetErrorDescription( $objSnmpManager.LastError )
    return $AXUNCERTAIN
  }

  $strData.value = $objSnmpObject.value
  if( $objSnmpObject.value -le $nMaxAllowed )
  {
    $strExplanation.value = 'SUCCESS: '
  }
  else
  {
    $strExplanation.value = 'ERROR: '  
  }
  
  $strExplanation.value = $strExplanation.value + 'IPs in use: [' + $objSnmpObject.value + ']'
  $objSnmpManager.Close()
  $objSnmpManager.Shutdown()

  # Note: type ID's are described in ActiveXperts Network Component manual, and included in the ActiveXperts Network Component samples.
  return $AXSUCCESS
}


#################################################################################
# // --- Main script ---
#################################################################################

# -- Clear screen and clear error
cls
$Error.Clear()

# -- Validate parameters, return on parameter mismatch
if( $strHost -eq '' -or $strSubnet -eq '' -or $nMaxAllowed -lt 0 )
{
  $res = 'UNCERTAIN: Parameter error - Usage: .\Dhcp.ps1 "<Hostname | IP>" "x.x.x.x" <nMaxAllowed>'
  echo $res
  exit
}

# -- Declare local variables by assigning initial value
$strData = ''
$strExplanation = ''
$objAltCredentials = $null
$strOID = '1.3.6.1.4.1.311.1.3.2.1.1.2.' + $strSubnet

# -- Check DHCP, assign to variable to prevent printing the function return value
$nRetVal = checkDhcpMaxInuse $strHost $strOID $nMaxAllowed ([ref]$strData) ([ref]$strExplanation)

# -- Print script result
echo $strExplanation
exit


#################################################################################
# // --- Catch script exceptions ---
#################################################################################

trap [Exception]
{
  $res = 'UNCERTAIN: ' + $_.Exception.Message
  echo $res
  exit
}