Introduction

Network Address Translation (NAT) and Bridged Networking are two essential networking configurations used in virtualized environments to connect virtual machines (VMs) to the external network. NAT-based port forwarding allows VMs to access external networks while keeping their private IP addresses hidden, whereas Bridged Networking connects VMs directly to the physical network, making them appear as individual devices on that network. This is an extensive guide on setting up NAT-based port forwarding and Bridged Networking in a virtual environment using popular hypervisors like VMware, VirtualBox, and Hyper-V.

Overview of NAT-Based Port Forwarding

NAT (Network Address Translation) is a method used to remap one IP address space into another by modifying network address information in the IP header of packets while they are in transit. NAT-based port forwarding allows external devices to communicate with a specific VM on a private network through a designated port on the host machine.

Benefits of NAT-Based Port Forwarding
  1. Security: VMs are isolated from the external network, reducing the attack surface.
  2. Simplified Network Configuration: No need to modify the physical network infrastructure.
  3. Ease of Access: External access to specific services on VMs through port forwarding.

Setting Up NAT-Based Port Forwarding in VirtualBox

  1. Open VirtualBox Manager.
  2. Select VM: Choose the VM you want to configure and go to Settings.
  3. Network Configuration:
    • Go to the Network tab.
    • Select Adapter 1 and ensure Attached to: is set to NAT.
  4. Port Forwarding Rules:
    • Click on Advanced.
    • Click on Port Forwarding.
    • Add a new rule by clicking the + icon.
    • Configure the rule:
      • Name: Give the rule a descriptive name.
      • Protocol: Choose TCP or UDP.
      • Host IP: Typically left blank to bind to all interfaces.
      • Host Port: The port on the host machine to forward (e.g., 8080).
      • Guest IP: The IP address of the VM (e.g., 10.0.2.15).
      • Guest Port: The port on the VM to forward (e.g., 80).
    # Example command for configuring port forwarding in VirtualBox CLI
VBoxManage modifyvm "VM name" --natpf1 "webserver,tcp,,8080,,80"

Setting Up NAT-Based Port Forwarding in VMware Workstation

  1. Open VMware Workstation.
  2. Select VM: Choose the VM you want to configure and go to Settings.
  3. Network Adapter Configuration:
    • Select the Network Adapter settings.
    • Ensure NAT is selected.
  4. Edit NAT Settings:
    • Go to Edit > Virtual Network Editor.
    • Select the NAT network and click NAT Settings.
    • Click Port Forwarding and add a new rule.
      • Host Port: The port on the host machine to forward (e.g., 8080).
      • VM IP Address: The IP address of the VM (e.g., 192.168.248.128).
      • VM Port: The port on the VM to forward (e.g., 80).
    # Example command for configuring port forwarding in VMware CLI
vmrun -T ws configurePortForwarding "NAT" "add" "tcp" "webserver" "8080" "192.168.248.128" "80"

Setting Up NAT-Based Port Forwarding in Hyper-V

  1. Open Hyper-V Manager.
  2. Select VM: Choose the VM you want to configure and go to Settings.
  3. Network Adapter Configuration:
    • Select the Network Adapter settings.
    • Ensure the adapter is connected to the NAT switch.
  4. Port Forwarding Configuration:
    • Open PowerShell as Administrator.
    • Create a NAT network if not already created:
    New-VMSwitch -SwitchName "NATSwitch" -SwitchType Internal
New-NetIPAddress -IPAddress 192.168.100.1 -PrefixLength 24 -InterfaceAlias "vEthernet (NATSwitch)"
New-NetNat -Name "NATNetwork" -InternalIPInterfaceAddressPrefix 192.168.100.0/24
    • Add port forwarding rule:
    Add-NetNatStaticMapping -NatName "NATNetwork" -Protocol TCP -ExternalIPAddress "0.0.0.0" -ExternalPort 8080 -InternalIPAddress 192.168.100.2 -InternalPort 80

Overview of Bridged Networking

Bridged Networking allows VMs to connect directly to the physical network, making them appear as separate devices on that network. Each VM gets its own IP address from the physical network’s DHCP server or can be assigned a static IP address.

Benefits of Bridged Networking
  1. Direct Network Access: VMs can access and be accessed by other devices on the same physical network.
  2. No Need for Port Forwarding: Each VM can use standard network ports without additional configuration.
  3. Full Network Functionality: VMs can perform all network operations like any physical machine on the network.

Setting Up Bridged Networking in VirtualBox

  1. Open VirtualBox Manager.
  2. Select VM: Choose the VM you want to configure and go to Settings.
  3. Network Configuration:
    • Go to the Network tab.
    • Select Adapter 1 and ensure Attached to: is set to Bridged Adapter.
    • Choose the appropriate network interface from the Name dropdown.
    # Example command for configuring bridged networking in VirtualBox CLI
VBoxManage modifyvm "VM name" --nic1 bridged --bridgeadapter1 "en0: Wi-Fi (AirPort)"

Setting Up Bridged Networking in VMware Workstation

  1. Open VMware Workstation.
  2. Select VM: Choose the VM you want to configure and go to Settings.
  3. Network Adapter Configuration:
    • Select the Network Adapter settings.
    • Ensure Bridged is selected.
    • Optionally, select Replicate physical network connection state.
    # Example command for configuring bridged networking in VMware CLI
vmrun -T ws modifyvm "VM name" -nic1 bridged

Setting Up Bridged Networking in Hyper-V

  1. Open Hyper-V Manager.
  2. Select VM: Choose the VM you want to configure and go to Settings.
  3. Network Adapter Configuration:
    • Select the Network Adapter settings.
    • Connect the adapter to a External virtual switch.
    • Create an external virtual switch if one does not exist:
    New-VMSwitch -Name "ExternalSwitch" -NetAdapterName "Ethernet" -AllowManagementOS $true
    • Attach the VM’s network adapter to the external switch:
    Set-VMNetworkAdapter -VMName "VM name" -SwitchName "ExternalSwitch"

Conclusion

NAT-based port forwarding and Bridged Networking offer distinct advantages and serve different use cases in virtualized environments. NAT-based port forwarding is ideal for scenarios where security and simplified network configurations are paramount, while Bridged Networking is suitable for situations requiring direct network access and full network functionality. By understanding how to set up and configure these networking options in VirtualBox, VMware, and Hyper-V, administrators can optimize their virtual environments to meet their specific networking needs.