Dhcp.vbs - Check DHCP scope through ActiveXperts Network Monitor
ActiveXperts Network Monitor ships with a powerful set of pre-defined checks. Each individual check has a static number of configuration items. To monitor other items, or to combine monitoring items, you can make use of custom VBScript checks.
Most of the built-in checks have a VBScript equivalent, implemented as a Function in a VBScript (.vbs) file. Out-of-the-box, each VBScript function monitors the same items as the built-in check. Feel free to modify a function. The VBScript check can be customized by editing the VBScript function.
To add a new VBScript-based DHCP monitoring check, do the following:
- On the 'Monitor menu', click 'New Monitoring Check (VBScript)'. The 'VBScript Check' dialog box appears;
- In the 'File selection box', select 'Dhcp.vbs';
- In the 'Function selection box', select 'CheckDhcpMaxInUse', 'CheckDhcpMaxOffered' or 'CheckDhcpMinAvailable';
- In the 'Function parameters group box' enter the required parameters. You can also load a working sample first by clicking on the 'Load a sample, click here' link.
To customize the above monitoring check, click on the 'Edit button' next to the 'File selection box'. Notepad will be launched. You can now make changes to the VBScript function(s).
Dhcp.vbs script source code
' ///////////////////////////////////////////////////////////////////////////////
' // ActiveXperts Network Monitor - VBScript based checks
' // (c) ActiveXperts Software B.V.
' //
' // For more information about ActiveXperts Network Monitor and VBScript, please
' // visit the online ActiveXperts Network Monitor VBScript Guidelines at:
' // https://www.activexperts.com/support/network-monitor/online/vbscript/
' //
' ///////////////////////////////////////////////////////////////////////////////
Option Explicit
Const retvalUnknown = 1
Dim SYSDATA, SYSEXPLANATION ' Used by Network Monitor, don't change the names
' //////////////////////////////////////////////////////////////////////////////
' // To test a function outside Network Monitor (e.g. using CSCRIPT from the
' // command line), remove the comment character (') in the following 5 lines:
' Dim bResult
' bResult = CheckSnmp( "localhost", "public", "1.3.6.1.2.1.1.5.0", "My Computer Name" )
' WScript.Echo "Return value: [" & bResult & "]"
' WScript.Echo "SYSDATA: [" & SYSDATA & "]"
' WScript.Echo "SYSEXPLANATION: [" & SYSEXPLANATION & "]"
' ////////////////////////////////////////////////////////////////////////////////////////
Function CheckDhcpMaxInUse( strDhcpServer, strSubnet, numMaxAllowed )
' Description:
' Check for maximum number of IP addresses in use.
' Requires SNMP running on the DHCP server and monitoring system.
' This function uses the Network Component, an ActiveXperts product.
' Network Component is automatically licensed when ActiveXperts Network Monitor is purchased
' For more information about Network Component, see: www.activexperts.com/network-component
' Parameters:
' 1) strDhcpServer - Host name or IP address of the DHCP server
' 2) strSubnet - Subnet.
' 3) numMaxAllowed - maxmimum number of IP addresses allows
' Usage:
' CheckDhcpMaxInUse( "<Hostname | IP>", "x.x.x.x", <maximum value> )
' Sample:
' CheckDhcpMaxInUse( "localhost", "192.168.31.0", 200 )
Dim strOID
CheckDhcpMaxInUse = retvalUnknown ' Default return value
SYSDATA = "" ' Not used by this function
SYSEXPLANATION = "" ' Set initial value
strOID = "1.3.6.1.4.1.311.1.3.2.1.1.2." & strSubnet
If( Not checkDhcpValue( strDhcpServer, strOID, SYSDATA, SYSEXPLANATION ) ) Then
CheckDhcpMaxInUse = retvalUnknown
Exit Function
End If
SYSEXPLANATION = "IP's in use: [" & SYSDATA & "]"
If( CInt( SYSDATA ) <= CInt( numMaxAllowed ) ) Then
CheckDhcpMaxInUse = True
Else
CheckDhcpMaxInUse = False
End If
End Function
' //////////////////////////////////////////////////////////////////////////////
Function CheckDhcpMaxOffered( strDhcpServer, strSubnet, numMaxAllowed )
' Description:
' Check for maximum number of IP addresses offered
' Requires SNMP running on the DHCP server and monitoring system.
' This function uses the Network Component, an ActiveXperts product.
' Network Component is automatically licensed when ActiveXperts Network Monitor is purchased
' For more information about Network Component, see: www.activexperts.com/network-component
' Parameters:
' 1) strDhcpServer - Host name or IP address of the DHCP server
' 2) strSubnet - Subnet.
' 3) numMaxAllowed - maxmimum number of IP addresses allows
' Usage:
' CheckDhcpMaxOffered( "<Hostname | IP>", "x.x.x.x", <maximum value> )
' Sample:
' CheckDhcpMaxOffered( "localhost", "192.168.31.0", 5 )
Dim strOID
CheckDhcpMaxOffered = retvalUnknown ' Default return value
SYSDATA = "" ' Not used by this function
SYSEXPLANATION = "" ' Set initial value
strOID = "1.3.6.1.4.1.311.1.3.2.1.1.4." & strSubnet
If( Not checkDhcpValue( strDhcpServer, strOID, SYSDATA, SYSEXPLANATION ) ) Then
CheckDhcpMaxOffered= retvalUnknown
Exit Function
End If
SYSEXPLANATION = "IP's offered: [" & SYSDATA & "]"
If( CInt( SYSDATA ) <= CInt( numMaxAllowed ) ) Then
CheckDhcpMaxOffered = True
Else
CheckDhcpMaxOffered = False
End If
End Function
' //////////////////////////////////////////////////////////////////////////////
Function CheckDhcpMinAvailable( strDhcpServer, strSubnet, numMinAvailable )
' Description:
' Check for minimum number of IP addresses available.
' Requires SNMP running on the DHCP server and monitoring system.
' This function uses the Network Component, an ActiveXperts product.
' Network Component is automatically licensed when ActiveXperts Network Monitor is purchased
' For more information about Network Component, see: www.activexperts.com/network-component
' Parameters:
' 1) strDhcpServer - Host name or IP address of the DHCP server
' 2) strSubnet - Subnet.
' 3) numMaxAllowed - maxmimum number of IP addresses allows
' Usage:
' CheckDhcpMinAvailable( "<Hostname | IP>", "x.x.x.x", <maximum value> )
' Sample:
' CheckDhcpMinAvailable( "localhost", "192.168.31.0", 10 )
Dim strOID
CheckDhcpMinAvailable = retvalUnknown ' Default return value
SYSDATA = "" ' Not used by this function
SYSEXPLANATION = "" ' Set initial value
strOID = "1.3.6.1.4.1.311.1.3.2.1.1.3." & strSubnet
If( Not checkDhcpValue( strDhcpServer, strOID, SYSDATA, SYSEXPLANATION ) ) Then
CheckDhcpMinAvailable = retvalUnknown
Exit Function
End If
SYSEXPLANATION = "IP's available: [" & SYSDATA & "]"
If( CInt( SYSDATA ) >= CInt( numMinAvailable ) ) Then
CheckDhcpMinAvailable = True
Else
CheckDhcpMinAvailable = False
End If
End Function
' //////////////////////////////////////////////////////////////////////////////
' //
' // Private Functions
' // NOTE: Private functions are used by the above functions, and will not
' // be called directly by the ActiveXperts Network Monitor Service.
' // Private function names start with a lower case character and will
' // not be listed in the Network Monitor's function browser.
' //
' //////////////////////////////////////////////////////////////////////////////
Function checkDhcpValue( strHost, strOID, BYREF numSysData, BYREF strSysExplanation )
Dim objSnmpManager, objConstants, objSnmpObject, strCommunity
checkDhcpValue = False ' Default return value
numSysData = 0 ' Not used by this function
strSysExplanation = "" ' Set initial value
strCommunity = "public"
' Create instance of SNMP object
Set objSnmpManager = CreateObject("ActiveXperts.SnmpManager")
Set objConstants = CreateObject ( "ActiveXperts.ASConstants" )
' Initialize SNMP object
objSnmpManager.ProtocolVersion = objConstants.asSNMP_VERSION_V2C
objSnmpManager.Initialize
If( objSnmpManager.LastError <> 0 ) Then
strSysExplanation = "Unable to initialize Network Component SNMP object"
checkDhcpValue = False
Exit Function
End If
' Open connection to (remote) SNMP agent
objSnmpManager.Open strHost, strCommunity
If( objSnmpManager.LastError <> 0 ) Then
strSysExplanation = "Unable to connect to agent [" & strHost & "] in [" & strCommunity & "] community. Be sure SNMP agent is running"
checkDhcpValue = False
Exit Function
End If
On Error Resume Next
Set objSnmpObject = objSnmpManager.Get( strOID )
If( objSnmpManager.LastError <> 0 ) Then
strSysExplanation = "Unable to retrieve [" & strOID & "]. . Be sure SNMP agent is running"
checkDhcpValue = False
Exit Function
End If
On Error Goto 0
numSysData = objSnmpObject.Value
strSysExplanation = "Value read: [" & objSnmpObject.Value & "]"
checkDhcpValue = True
' Note: type ID's are described in Network Component manual, and included in Network Component samples.
objSnmpManager.Close()
objSnmpManager.Shutdown()
End Function