ComTech: IT Support Stirling

Tutorial – How to Subnet

Today I will show you a technique I learnt for my Cisco exams on how to subnet and choosing subnet masks.

The best way to explain subnetting is by showing some examples.

Question 1:

If a subnet mask of were used with a Class A network how many subnets and hosts per subnet could exist?


The best way to answer this question is to break it down into individual sections.  The sections are:

1. No of Network bits

2. No of Host bits,

3. No of Subnet bits,

4. No of Subnets

5. Hosts per Subnet.

Lets take them one at a time.

No of Network bits = 8 (This is defined by Class A = 8, Class B = 16 and Class C = 24)

No of Host bits = 16 (This is defined by the number of zeros in the subnet mask)

No of Subnet bits = 8 (This is defined by 32 – No of network bits – No of Host bits)

No of Subnets =  256 (This is defined by  2ˆ No of subnet bits)

Hosts per Subnet = 65534 (This is defined by 2ˆNo of Host bits – 2)

So to answer the question  No of subnets = 256 with 65534 hosts per subnet.

Question 2:

Which of the following are valid subnet numbers in network when using mask




Again the best approach is to break the question down into sections.  This time the sections are:

1. Find the Subnet Number

2. Calculate the First address in the range

3. Calculate the Broadcast address

4. Calculate the last address in the range

Lets take them one at a time.

Subnet Number = (This is defined by 256 – 248 = 8 (Subnet Magic Number). 8 *0 = 0 (Interesting Octet) which is the closest multiple <=0 which is the 3rd octet in

First number in the address range = (This is defined by adding 1 to the subnet’s last octet)

Broadcast Address = (This is defined by the Subnet Magic Number (8) + Interesting Octet (0) minus 1

Last address in the range = (This is defined by the broadcast address -1)

So to answer the question the subnet numbers begin with (zero subnet) and then, and so on therefore a and c are the correct answers.

I hope that the steps outlined above help when it comes to subnetting your own networks.

About the Author


Hi I’m Chris Wakefield the owner of ComTech IT Support. I provide Windows, Mac and Linux based IT Support to small businesses in Stirling, Alloa and Falkirk.

Follow @Comtech247 on Twitter

Clonezilla Tutorial

Today we are going to take a look at how you would clone a system and deploy it on another computer. To do this we will use the open source software Clonezilla. I have been using Clonezilla for a couple of years and found it to be a very versitile piece of software and ideal when cloning systems (and its free!!).  For the purpose of this tutorial I will be using Windows 7 and Clonezilla running from a live cd.

Before you use Clonezilla (only use this section if you intend to deploy to new systems otherwise skip to live CD)

You have to prepare your Windows system before you can clone it.  The first thing to do is to add all the applications you want on the new system.  Once you have done that we need to remove all the unique identifiers (e.g passwords, activation codes etc).  For that we need sysprep.

Go to:

Start – Computer – Local Disk (C:) – Windows – System32 – sysprep – sysprep

Once you start sysprep you should get the screenshot  below.

Make sure that you set the System Cleanup Action to OOBE and that the generalize box is ticked.  You should also set Shutdown Options to Shutdown.  Once configured click ok. This will start the sysprep tool and once complete will shut down the system.

Starting Clonezilla

It is time to boot the system from the Clonezilla live cd.  On the startup screen leave the default and press return.

On the next screen you will be asked to pick your language.  Press return when you have chosen.

On the next screen you will be asked for your keymap configuration.  Unless you know what you are doing I would recommend you don’t touch this and use the Don’t touch keymap option.

You will now be asked if you would like to start the Clonezilla software or enter a shell (for those so inclined).  For the purpose of this tutorial chose Start Clonezilla.

We will now be asked where we would like to save the cloned system image file. Clonezilla gives you several options of where to store the file.  For the purpose of this tutorial I will store it on a local device (ie my 16Gb usb penstick).  When you have decided where to store the image press return and Clonezilla will mount the device.

On the following page you need to configure a device as /home/partimag.  Chose the same device that you mounted to store your image on so in my case it will be sdb1 as this is my 16Gb usb penstick.

The next option you will have to configure is where on your device do you want to store your image.  As you can see from the screenshot below I have a lot of files and folders on the usb penstick.  If you don’t want the image stored in a specific folder then pick / and press return.

After deciding where to store the image file Clonezilla lets you configure advanced features and options by means of a wizard.  You will need to decide if you want the Beginner or Expert wizard.  Chose Beginner unless you have some specific options that you want to configure as this is sufficient for most peoples needs.

On the next page of the wizard you want to choose savedisk as this saves the local disk as an image for you to deploy later.

When presented with the next screen you have to enter a name for your image as shown below.

Clonezilla will now ask you to pick the source disk that should be imaged.  If your computer only has one disk then Clonezilla will highlight it for you.  If you have multiple disks then you will have to choose which one you want to image.

To make sure your image is restorable choose Yes check the saved image as shown below.

Now we come to the final screen shown below.  Check that you are happy with the choices shown and when ready press Enter.  Your hard disk will now be imaged and saved in the location you specified earlier.  You will need to be patient as this can take some time depending on the size of your hard drive.

If you found this blog useful then why not sign up to my RSS Feed for news, tutorials, views and general techie stuff!!

About the Author


Hi I’m Chris Wakefield the owner of ComTech IT Support. I provide Windows, Mac and Linux based IT Support to small businesses in Stirling, Alloa and Falkirk.

Follow @Comtech247 on Twitter



Teamviewer Tutorial

Today we shall have a look at a piece of remote desktop software called Teamviewer. Teamviewer is the software that we use to connect to our client’s computers remotely and solve any problem they might have.

Teamviewer can be installed from here and works on all the major platfroms.  Once installed you will get a view identical to the one below.



Teamviewer console displayed on Linux Mint 12



You will notice that Your ID and Password are displayed.  You must give this information to the person who will be taking control of your system.  The Id of your computer will not change, however the password will change after every session thus removing the possibility of anyone getting onto your computer without your knowledge.  Once a session has been established the client (the person who is getting the help) can retake control of their computer at any time by moving the mouse.

You will also notice that you have a choice of either remote control or file transfer.  On Windows systems Teamviewer 7 also allows VPN connection (discussed below).  File transfer is very handy when you have to transfer files over the internet quickly.

VPN connection

First we have to set up an unattended session which will allow us to log onto another computer with a specified password even if no one is in attendance. On the main console page you will Set up an unattended session which is located underneath Password.  Click on this and enter the required details.

Once this is set up I always find it easier to setup a teamviewer account.  There are two reasons for this.  The first reason is I can then vpn into my systems using a web browser which can be convenient when you are out and about.  The second is that the web interface allows me to manage all my accounts in one place.  You can set up a teamviewer user account here and click on web login.  Once completed you should get the screen displayed below.

All the computers that you have already setup will be visble in the top left of the screen under My Computers.  You can add further computer accounts using the web interface by clicking on Add new partner which will then give you the screen below.

Change the Partner type to Compuer (as shown) and Group to My Computers (as shown). Fill in the ID and Alias as appropriate.  The password is not the teamviewer password but any password you choose.  Once completed the new partner will be visible in the top left of the screen under my computers.  To connect to it just double click.

So to round off Teamviewer is a very versitile piece of software that allows you to take control of another computer by either a web based interface or your own computer.  Go and have a play and see what you think.

About the Author

Hi I am Chris Wakefield the owner of ComTech IT Support. I provide Windows and Linux based IT Support, laptop repairs and computer repairs to both business and personal clients in and around Stirling.

For a list of what I can offer you why not visit my website where you will find a list of my services, testimonials, blog and much more.

FreeNAS Tutorial

I have been playing around with old hardware recently and one of the things I have done is install and set up FreeNAS NAS storage. This tutorial will show you how.

Before we do anything you must first find out your network configuration.  In windows open up a command prompt and type ipconfig /all. In Linux open up a terminal and type ifconfig. Write down your IPv4 address, default gateway, subnet mask and DNS servers as we will be using this information later.

Now we need to get our hands on a copy of FreeNAS. The most recent version is 8 and you can get it here.  Once downloaded burn a copy to CD.  The next thing you have to do is decide where you are going to install it.  I chose an old computer I had lying around (thanks Rob) but you could just as well install it within a virtual machine. The computer had 10Gb of storage and I installed another 1.5Tb.  FreeNAS can be installed on a USB penstick thus saving your hard drive for network storage but since I had the 10Gb disk I used that instead.

Insert the CD into your computer and allow the software to install.  Once installed you will arrive at the console setup which will give you the URL to access your installation via a web interface.  For example mine was

Open up your browser of choice and enter your FreeNAS URL.  When prompted the default username and password are:

admin and freenas (we will be changing this later)

You will then be faced with the FreeNAS interface where you can configure your server.


The first thing you need to configure is your network interface and you do this by using the network tab.  Click on the network tab and you will be presented with more settings.  In Global Configuration choose a hostname, enter your default gateway (e.g and your nameserver (usually the same as your default gateway).  Once done press ok.  Next click on Interfaces and then add interface.  You need to set your IPv4 address as static so it doesn’t change. So for example my network goes from – so I chose  When you set this the web interface from now on will always be the address you enter so mine is now set to  Also set your netmask.  Mine was (so /24).


Next thing we need to do is set the users who will be able to access our shares.  Click on Account (left menu) and go to Users – add user.  Add a username and a password (make sure this is the same as the user on your computer that will be accessing the shares).  Now expand Account – Groups – add group and add a new group who will be able to access the shares. Final thing is to add your username to the new group.  Click on Account – Groups – view all groups and then find the new group and click on members.  Add yourself to the new group.


Now we come to adding your storage.  Click on the storage tab and then add volume. Choose volume name, disk and filesystem type (use ZFS).  Once done click add volume.  The disk should now be visible with ONLINE next to it.  Next we need to set the permissions.  Click on Change Permissions and then chose who owns the file (should be set to your username). Then in owner group add the group you set up earlier and then set the permissions as required.  Once completed press save.


We will now set up the shares.  Click on the sharing tab.  If you will be sharing to Windows machines click on Windows, Apple for Apple and Unix for Linux.  Add the share and set up as required.


We now have to make sure that we can see the shares over the network.  Click on the services tab at the top of the screen.  For windows turn on CIFS and for Linux NFS.

Your FreeNAS server is now set up.

Accessing Shares over the network

For windows: right click on computer (Windows 7) and select map network drive.  Browse for the share.

For Linux: enter the following line into the fstab file /mnt/MyDisk1 /media/dev/MyDisk1 nfs hard, 0 0


  • is the static address of your FreeNAS server
  • /mnt/MyDisk1 is the path to your FreeNAS storage
  • /media/dev/MyDisk1 is the mount point
  • nfs is the filesystem

One final thing is to change the default password to the web interface.  To do this expand Account – My Account – Change Password and enter your new password.  Do not forget this!!

About the Author

Hi I am Chris Wakefield the owner of ComTech IT Support. I provide Windows, Linux and Mac based IT Support to small businesses throughout the Stirling, Falkirk and Alloa areas.

For a list of what I can offer you why not visit my website where you will find a list of my services, testimonials, blog and much more.




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