I have found myself spending more time than I should configuring Vagrant networking with my Vagrant files and VirtualBox over the past year and figured it was about time to put some of this knowledge down somewhere.

Public Networking

Public networking allows your vagrant machines to be allocated IP addresses as if they were physical devices on your network: config.vm.network "public_network", you also can attempt to manually set the IP address yourself config.vm.network "public_network", ip: "192.168.0.17".

Pros

  • Your VMs are available to the wider network making for easy access to development stacks
  • IP allocation if using the defaults will be handled for you, no hassle

Cons

  • Uses up IP allocation on your network via DHCP
  • Vagrant’s use of a default insecure key and password for the vagrant user means your VMs will be exposed unless you stake explicit steps to secure them.
  • Manually specifying the IP address in public networking rarely seems to work in my experience/configuration.

Private Networking

Private networking allows you to provide your machines with IP addresses within the vagrant subnet (192.168.33.x)
You can either specify these yourself config.vm.network "private_network", ip: "192.168.33.25".
Or you can allow vagrant to assign these itself config.vm.network "private_network", ip: "auto".
If you want external access on a port then port forwarding is required: config.vm.network "forwarded_port", guest: 80, host: 8080.

Pros

  • Control over IP address allocation if you want it
  • As they are on the same subnet inter-VM communication just works
  • No DHCP IP allocation issues on the wider network
  • No external systems can access your VM over the network

Cons

  • IP Address clashes - if you don’t keep track of addresses you’ve allocated and the machines you’re running then your chances of getting an IP address clash go up.
  • Lack of external access
  • Requires port forwarding from host to guest OS if you require access beyond SSH

MAC address static IP allocation.

Technically this is a subset of public networking but has proven to be more useful than trying to use the static IP option. What I do is set up a public network then bridge the adapter and specify a MAC address for the virtual machine.

An example of a Linux / Mac OS bridge:
config.vm.network "public_network", :mac => "080027D3418E, :bridge => "en1: Wi-Fi (AirPort)"

An example of a Windows bridge:
config.vm.network "public_network", :mac => "080027D3418E", :bridge => "Realtek PCIe GBE Family Controller"

I find myself creating a define section (config.vm.define "profile_name" do |profile_name|) in the vagrant config for each physical machine as the bridging requires the OS level name of the network adapter, this can be found using ifconfig on linux/Mac OS and ipconfig /all for Windows.

Now in my router settings I can configure a static IP based on MAC address (and even port forwarding should I wish), ensuring that I can host services from my vagrant files and will find them at a consistent IP address allowing me to use a modified hosts file to alias this address to a nice readable/memorable domain.

Pros

  • You can allocate an IP address at the router level to ensure you get the same IP address each time
  • Combining defined profiles with the MAC address and physical networking adapters allows for creation of dev, test etc environments at fixed places on particular machines.

Cons

  • There is very little documentation around about using bridged adapters, support varies across VM providers as well it seems.
  • Not portable across physical machines or OS’s as they will have different named networking adapters

Aside

I’m currently making use of all the above vagrant networking styles as each has a strength and weakness. Typically for services I’m hosting on a small Dell server I’ll allocate an IP address to MAC addresses for each VM, I then maintain a little network diagram so I’m aware of the MACs and IPs I’m using. For writing puppet modules I tend to stick with private networking and for proof reading and viewing layout of this blog I’ll do a private network with an allocated ip.