1 Objective

You will use the Port Forwarding network feature of Virtual Box, and configure it to access your guest VM via SSH.

2 Why Port Forwarding ?

By default your VM is created with a network connection in NAT mode.

We have discussed this earlier, but as a reminder:

Everything is fine while you are using the console, as we have done so far, but what if you want to:

3 Using Port Forwarding

To enable port forwarding, open the settings for your Virtual Machine.

Verify that NAT is selected in the Attached to: selector.

At the bottom of the window, click on the Port Forwarding button.

You are then presented with a form where you can add new forwardings.

3.1 Addding a forwarding

What we are going to do is pick a port on our Host, for example 2222, and forward TCP connections received on this port, to port 22/TCP (SSH) on our guest.

To do this, click on the green (+) button on the right.

Once you click it, a new row appears, ready to be filled out:

Fill it out as follows:

Name Protocol Host IP Host Port Guest IP Guest Port
SSH TCP 2222 22


What the above rule means is:

"If a TCP connection is received on the Host on TCP port 2222, send it on to the Guest on TCP port 22"

To apply the changes, click OK.

You are back in the Network Settings windows. Click OK again to exit the Network Settings.

You will probably need to restart the Virtual Machine so that the changes are applied:

3.2 Testing the forwarding

To verify that the change has been implemented:

netstat -a | more

Use the space bar to move one page at a time, and look for a line similar to this:

tcp4       0      0         *.*                    LISTEN


tcp4       0      0  *.2222         *.*                    LISTEN

This means that your Host is listening on port 2222 for connections.

3.3 SSH to the Guest

Now, it's time to try and connect to the Guest.

To do so, use the Putty terminal emulator (if you are on Windows). For Linux and Mac users, use the built in terminal.

You need to remember the username you created on your Guest! Remember, you CANNOT log in as root using SSH, so this will have to be the user you created.

If using Windows:

If everything goes well, you will be prompted to accept the Host Key. Click 'Yes'. We will discuss this in class.

You will then be prompted to login as:. Here you will enter the username you created previously.

If using Linux or OS X:

... remember to replace _username_ with the user you created!

You will be prompted to accept the host key:

The authenticity of host '[]:2222 ([]:2222)' can't be established.
RSA key fingerprint is ef:f3:e6:01:67:44:e4:3d:57:4a:64:80:f1:41:53:8c.
Are you sure you want to continue connecting (yes/no)? yes

You will then be prompted to enter the password for the username:

_username_@'s password:

Enter your password.

You should now be logged in!

3.4 Optional

Ask other participants to log into your VM - you will provide them with two parameters:

  1. If you want to disable this, and only allow connections coming from your Host to talk to the Guest, then put instead. via the forward.