»Private Networks

Network identifier: private_network

Vagrant private networks allow you to access your guest machine by some address that is not publicly accessible from the global internet. In general, this means your machine gets an address in the private address space.

Multiple machines within the same private network (also usually with the restriction that they're backed by the same provider) can communicate with each other on private networks.

»DHCP

The easiest way to use a private network is to allow the IP to be assigned via DHCP.

Vagrant.configure("2") do |config|
  config.vm.network "private_network", type: "dhcp"
end

This will automatically assign an IP address from the reserved address space. The IP address can be determined by using vagrant ssh to SSH into the machine and using the appropriate command line tool to find the IP, such as ifconfig.

»Static IP

You can also specify a static IP address for the machine. This lets you access the Vagrant managed machine using a static, known IP. The Vagrantfile for a static IP looks like this:

Vagrant.configure("2") do |config|
  config.vm.network "private_network", ip: "192.168.50.4"
end

It is up to the users to make sure that the static IP does not collide with any other machines on the same network.

While you can choose any IP you would like, you should use an IP from the reserved private address space. These IPs are guaranteed to never be publicly routable, and most routers actually block traffic from going to them from the outside world.

For some operating systems, additional configuration options for the static IP address are available such as setting the default gateway or MTU.

»IPv6

You can specify a static IP via IPv6. DHCP for IPv6 is not supported. To use IPv6, just specify an IPv6 address as the IP:

Vagrant.configure("2") do |config|
  config.vm.network "private_network", ip: "fde4:8dba:82e1::c4"
end

This will assign that IP to the machine. The entire /64 subnet will be reserved. Please make sure to use the reserved local addresses approved for IPv6.

You can also modify the prefix length by changing the netmask option (defaults to 64):

Vagrant.configure("2") do |config|
  config.vm.network "private_network",
    ip: "fde4:8dba:82e1::c4",
    netmask: "96"
end

IPv6 supports for private networks was added in Vagrant 1.7.5 and may not work with every provider.

»Disable Auto-Configuration

If you want to manually configure the network interface yourself, you can disable Vagrant's auto-configure feature by specifying auto_config:

Vagrant.configure("2") do |config|
  config.vm.network "private_network", ip: "192.168.50.4",
    auto_config: false
end

If you already started the Vagrant environment before setting auto_config, the files it initially placed there will stay there. You will have to remove those files manually or destroy and recreate the machine.

The files created by Vagrant depend on the OS. For example, for many Linux distros, this is /etc/network/interfaces. In general you should look in the normal location that network interfaces are configured for your distro.