This guide installs Debian 9.5 on VMWare using a virtual network bridge and NAT within iptables to isolate the virtual machine from connecting to other machines on local network, while still allowing outside connectivity. Only udp DNS requests are allowed from virtual machine to local network.

Step 1: Setup virtual network bridge

Create a virtual network bridge:

$ sudo apt-get install bridge-utils
$ sudo brctl addbr vnet1

List network bridges:

$ brctl show

Setup network interface:

$ sudo nano /etc/network/interfaces

Add the following:

auto vnet1
iface vnet1 inet static
    bridge_ports none
    bridge_maxwait 0
    bridge_fd 1

Start the virtual network interface:

$ sudo ifup vnet1

Check network status using:

$ ifconfig

Local network eth0 configured as follows:

  • IP:
  • Gateway:

Step 2: Configure iptables forwarding

Enable forwarding:

$ sudo echo 1 > /proc/sys/net/ipv4/ip_forward

Add the following to iptables rules:

# vnet1: drop new connections to local machine
-A INPUT -s -m conntrack --ctstate NEW -j DROP

# vnet1: accept solicited packets in
-A FORWARD -i eth0 -o vnet1 -m conntrack --ctstate ESTABLISHED,RELATED -j ACCEPT

# vnet1: forward related packets out
-A FORWARD -i vnet1 -o eth0 -m conntrack --ctstate ESTABLISHED,RELATED -j ACCEPT

# vnet1: forward packets (except those going to local network)
-A FORWARD -i vnet1 -o eth0 ! -d -j ACCEPT

# vnet1: forward dns requests (to local interface)
-A FORWARD -i vnet1 -o eth0 -p udp --dport 53 -j ACCEPT

# reject everything else

Within nat section of iptables rules:


Step 3: Install Debian 9.5 netinst

Grab the latest amd64 image from

Within VMWare Workstation, open Edit => Virtual Network Editor, click Add Network..., choose Bridged, click Add.

For vmnet3 adapter, created above, set bridged to vnet1, click Save.

Within VMWare Workstation, open File => New Virtual Machine, choose I will install the operating system later, click Next.

Choose Linux as operating system, specifying the latest Debian version, click Next.

Choose Name and Location of virtual machine, click Next, use defaults for disk, click Next, click Customize Hardware....

Under Device choose New CD/DVD (IDE). Change Use a physical drive to Use ISO image, click Browse... and select the install image downloaded above.

Under Device choose Network Adapter. Change NAT to Custom: Specify virtual network, select /dev/vmnet3.

Click, Close, click Finish.

Power on and complete the installation, creating a new user account anon, then reboot.

Step 4: Setup network interface

Determine network interface:

$ sudo ifconfig

Stop network interface:

$ sudo ifdown ens33

Since no DHCP server was installed, setup network interface with static IP:

$ sudo nano /etc/network/interfaces

Add the following:

auto ens33
iface ens33 inet static

Update resolv.conf to reflect correct DNS server:

$ sudo nano /etc/resolv.conf

Change nameserver to correct IP address:


This is the router on the local network which we forward DNS traffic from the virtual machine to.

Start network interface:

$ sudo ifup ens33

That’s it!

Extra: System packages & commands

$ apt-get install lsof vim ca-certificates ssh

To show listening programs:

$ lsof -i

To see local network ip:

$ ip route show