Vagrant: can not ping guest machine from the host

Question

I have Mac OS with installed vagrant. On guest machine I have Ubuntu 12. So, what I would like to do is ping guest machine from host.

Guest machine attached to NAT (according to VirtualBox settings)

I found only one interface on guest machine (except lo):

eth0      Link encap:Ethernet  HWaddr 08:00:27:88:0c:a6  
          inet addr:10.0.2.15  Bcast:10.0.2.255  Mask:255.255.255.0
          inet6 addr: fe80::a00:27ff:fe88:ca6/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:581 errors:0 dropped:0 overruns:0 frame:0
          TX packets:410 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:61376 (61.3 KB)  TX bytes:51599 (51.5 KB)

The thing is that there is not ip address in 10.0.2.* network on the host. Host machine has several vboxnet interfaces, but they all don't have any ip addresses:

vboxnet0: flags=8842<BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
          ether 0a:00:27:00:00:00 
vboxnet1: flags=8842<BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
          ether 0a:00:27:00:00:01 
vboxnet2: flags=8842<BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
          ether 0a:00:27:00:00:02 
vboxnet3: flags=8842<BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
          ether 0a:00:27:00:00:03 

Have you got any idea why ip address is not assigned to host machine by VirtualBox? What can I do to be able to ping gust machine?

Here is my vagrant file (I removed some commented lines which I do not use):

# -*- mode: ruby -*-
# vi: set ft=ruby :

# Vagrantfile API/syntax version. Don't touch unless you know what you're doing!
VAGRANTFILE_API_VERSION = "2"

Vagrant.configure(VAGRANTFILE_API_VERSION) do |config|
# All Vagrant configuration is done here. The most common configuration
# options are documented and commented below. For a complete reference,
# please see the online documentation at vagrantup.com.

# Every Vagrant virtual environment requires a box to build off of.
config.vm.box = "hashicorp/precise64"

# The url from where the 'config.vm.box' box will be fetched if it
# doesn't already exist on the user's system.
# config.vm.box_url = "http://domain.com/path/to/above.box"

# Create a forwarded port mapping which allows access to a specific port
# within the machine from a port on the host machine. In the example below,
# accessing "localhost:8080" will access port 80 on the guest machine.
config.vm.network "forwarded_port", guest: 80, host: 8080
config.vm.network "forwarded_port", guest: 3306, host: 8086
config.vm.network "forwarded_port", guest: 27017, host: 27017

config.vm.synced_folder "/Users/KoulSlou/Documents/Cloudware12.10", "/vagrant", owner:     "www-data", group: "www-data"
config.vm.synced_folder "/Users/KoulSlou/Documents/Cloudware/public","/cloudware", owner: "www-data", group: "www-data"

# Create a private network, which allows host-only access to the machine
# using a specific IP.
#config.vm.network "private_network", ip: "192.168.1.2"

# Create a public network, which generally matched to bridged network.
# Bridged networks make the machine appear as another physical device on
# your network.
# config.vm.network "public_network"

# If true, then any SSH connections made will enable agent forwarding.
# Default value: false
# config.ssh.forward_agent = true
...

end

Answer 1

By default (i.e. when not touching any network configurations), Vagrant configures VMs in VirtualBox to attach their first interface (eth0) to "NAT" (don't confuse it with "NAT Network" which is different option in VirtualBox).

When your VM interface is attached to NAT, the guest will get 10.0.2.15 IP. On the host side you will only see vboxnet# interface without IP. You can think about this interface as a private router for that guest.

VMs that are connected to NAT are not routable from the outside world. This is by design and that's one of the reasons why vboxnet# interface has no IP. VMs are able to access the "outside world" such as the internet and host machine but cannot be accessed from the outside world without port forwarding.

If default behaviour is not what you looking for, Vagrant provides high level abstraction of networking config:

1. Private network - This will create new subnet that shouldn't collide with host's subnet (or any other subnets the host might have route to). In VirtualBox this will be configured by attaching additional interface to "Host-Only".
2. Public network - Your VMs will get IP from the same subnet as your host. Basically this is like creating new machine on the same network as your host. In VirtualBox this will be configured by attaching additional interface to "Bridged Adapter".

More advanced networking configurations are possible by configuring networking via provider specific configuration.

Each config has it's own pros and cons and it's really depends on what you plan to achieve. For additional info check VirtualBox's docs about networking.