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DHCP MAC filtering on Windows Server 2003 and 2008 R1

Recently I needed to setup MAC filtering on our DHCP server and being familiar with Windows Server 2008 R2 I thought it was a standard feature.  However I couldn’t be more wrong.  It turned out none of the previous server versions had this feature.  So after a little searching I found an addon from Microsoft Technet that does the trick.  It is called DHCP Callout.  It is an MSI for 32 and 64 bit operating systems. So the installation is easy but it took me a minute to figure out how to configure it.

So after the installation you can access the files in the C:\Windows\system32\dhcp.  In that directory a few files are installed.

  • MacFilterCalloutErrorlog.txt
  • MacFilterCalloutInfolog.txt
  • MACList.txt
  • SetupDHCPMacFilter.txt

It adds log files, a config file, and a setup document.  It also adds a few registry entries in HKLM\System\CurrentControlSet\Services\DHCPServer\Parameters.  These entries are as follows.

  • CalloutDlls                                   –  This specifies the dll path for the dhcp server
  • CalloutEnabled                           –  This loads the dll
  • CalloutErrorLogFile                   –  Specifies the Error log path
  • CalloutInfoLogFile                      –  Specifies the Info log path
  • CalloutMACAddressListFile     –  Specifies the name and location of MAC filter list

This is all covered in the setup guide as well.  To setup the MAC filter list is pretty simple as well.  You simply take you MAC addresses without and colons, dashes, or spaces and add them to the MACList.txt file.  However at the top of the file you have to tell the DHCP server to allow or deny the MAC addresses that you have entered.  Below is an example of the MAC filter list.

MAC_ACTION = {ALLOW}  or DENY
0001a0c00d54
0001a0c10d35

We used this to improve security and to keep machines that are not ours off our DHCP server.  All in all this works well.  We found this out when we couldn’t get some of our systems to pick up an IP address from our server.  Turns out we forgot to add them to the list.  Anyhow we no longer have problems with systems controlled by another group of admins using up our IP space.  So if you find this may be something that you are looking for you can download it at the following address.

http://blogs.technet.com/b/teamdhcp/archive/2007/10/03/dhcp-server-callout-dll-for-mac-address-based-filtering.aspx

 

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Tweaks to make Ubuntu 12.04 LTS the perfect Linux desktop

 

I recently install Ubuntu 12.04 on a older system to try it out.  I will say that I was truly impressed with the functionality of this distro.  First lets start with the specs of the machine I used.  It was an Acer 3850 with a single core 1.86 GHz processor , 3 gigs of 666 MHz memory, and a 60 gig SSD hard drive.  I also install the 64 bit version.  I have been using Linux for almost a decade now and by far this is one of the best GUIs I have ever used.

Once it was installed you have to setup a few things to add some creature comforts.  First I had to get my wireless to work correctly.  The laptop had a Broadcom wireless card so I had to install the Third party driver.  Here is the syntax to install I used to install the driver.

  • sudo apt-get install b43-fwcutter
  • sudo apt-get install firmware-b43-installer
  • If you have a legacy device you may need to us this instead:    sudo apt-get install firmware-b43legacy-installer
  • sudo modprobe b43

I still had a problem getting the driver to work when I rebooted the device so I had to add the modprobe b43 to the a file that I will update the name once I get the right name.

Then I added Unsetting.  This gives you a GUI that can be used to change certain aspects of the Unity interface.

  • sudo add-apt-repository ppa: diesch/testing
  • sudo apt-get update
  • sudo apt-get install unsettings

Then I added weather to the menu bar.  I like to have easy access to it.  This can be done with a simple command.

  • sudo apt-get install indicator-weather

Finally i like to have the System Monitor in the menu bars as well.  You will need to install another package using apt-get.

  • sudo add-apt-repository ppa:indicator-multiload/stable-daily
  • sudo apt-get update
  • sudo apt-get install indicator-multiload

I did have to get use to the fact that you need to search the programs you are looking by using the Dash Home icon.  But it is really easy to use and anyone can figure it out.  However you do need to have an idea of what you are looking for.  One other thing that really makes this easy to use is the Ubuntu Software Center.  This makes it really easy for anyone to install applications to the OS.  Installing applications on other versions of Linux is one of the problems that Windows users have.  Let me put it this way, my 6 year old figured out how to use this and really likes how this OS works.  Plus if Windows keeps going in the direction it is going I can see myself moving to Ubuntu as my primary OS used on my computer.

  Anyhow here are some must have programs that I would install to make Ubuntu a little more user friendly.  First I would install VLC, everyone has heard of it and it is one of the best video players.  Second would be Wine.  This is a program that allow you to install some Windows programs into Linux.  This works great and I use it for programs like Photofitre, which is a graphics editor.  I just like using this program even though you can use Gimp.  Finally I like to install some games.  This would include Assault Cube, Battle for Wesnoth, and xScorch.  Great for stress relief and killing time.

  I also like Libre Office and it works with MS Office docs so it is very functional.  Plus the long term support will keep your computer patched for years to come.  This may also be another way to squeeze more years out of that old computer that will not run the newer Windows versions.  If you are looking to try something different you may want to try this easy to use version of Linux.  I think this could be the version of Linux that has a change to really cut into the Windows market.  It also runs as a LiveCD if you just want to try it.  Plus it has a built in boot loader program that will allow you to easily set up a dual boot system with Windows.  Give it a shot.  Go to Ubuntu.com to download it.  Ubuntu 12.10 is now out and it is suppose to have several improvements.

 

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Sending Messages to Remote Workstations with a Script

Recently we had been working on scripting to make our live a little easier at work.  One of the projects was the ability to send messages to users that are in other buildings or everyone.  So after a few minutes of playing I got it to work and I thought I would share it with everyone.  The script is a batch file that allows you to type in the message that you want to send out to the users.  Then this batch file creates a VB Script that will be used to create the nice popup window on the remote machine.  I have it writing the VBS script to a share to be accessed by the computers.  So here it is.

@echo off
echo ***********************************************************
echo             Tech Control Messaging System
echo ***********************************************************
echo.
echo.
echo      Enter the message you want to send out to the
echo      workstations at the prompt below.
echo.
echo.
echo.
set /p _mes=Enter the message:
echo x=msgbox (“%_mes%” ,64, “Messaging System” )  >  c:\”share name”
psexec.exe @nodelist.txt -i -s -d wscript.exe \\”share name”\message.vbs

As you can tell it uses PsExec to connect to the systems.  We use this with Windows 7 with out a problem.  The VB Script creates a popup window with a warning icon and a OK button.  This script also uses a list of computer names to send the message to called nodelist.txt.  I am sure there are plenty of other ways to get the computer names but I like this way.   The message window will look similar to the following picture:

If you don’t have a way to send out messages to users this is a good start.  I hope this helps someone.

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