How to emulate Internet in multi machine environment with Vagrant - virtual-machine

Question

I'm creating a vagrant multi machine configuration file. Here is a chunk:
Vagrant.configure(2) do |config|
config.vm.box = "chef/centos-7.0"
config.vm.define "radius" do |radius|
radius.vm.hostname = "radius-server"
end
config.vm.define "mysql" do |mysql|
mysql.vm.hostname = "mysql-server"
end
end
how can I emulate the situation in which the above two virtual machines are in different networks separated by Internet?
I could create two different private networks having two different private ip addresses like 192.168.1.3 for the first virtual machine and 192.168.2.3 for the second virtual machine. in this case the machines would be in different networks. But could they talk to each other?

Answer 1

Yes, they can talk.
You need a router (the 3rd node) connected to both of these networks.
The router acts as the (mini) Internet:
A=[192.168.1.3] <=> [*.*.1.1]=router=[*.*.2.1] <=> [192.168.2.3]=B
Details
The easiest way is to assign the router role to the physical host because it has IP addresses on both of these networks (I guess they are 192.168.1.1 and 192.168.2.1 in your example). Otherwise, they are just numbers and, if Vagrant does not complain, network will function with IP addresses from public ranges as well (just be careful to disconnect physical network for clean testing).
Just enable routing (forwarding) in the OS on the physical host - googled example for Linux.
And make sure routes are configured on both of the virtual machines to each other via this router:
A's shell> ip route add default via 192.168.1.1
B's shell> ip route add default via 192.168.2.1
NOTE: Technically, because the networks use private IP addresses, they are not routable on the Internet (AFAIK, real Internet routers drop packets with these private IP addresses, while home routers NAT them).
Working Vagrant file
Tested example using libvirt provider.
Note that VMs are connected to two different networks.
VAGRANTFILE_API_VERSION = "2"
Vagrant.configure(VAGRANTFILE_API_VERSION) do |config|
config.vm.provider "libvirt"
config.vm.define "rhel7_minion" do |rhel7_minion|
rhel7_minion.vm.box = "uvsmtid/centos-7.1-1503-gnome"
rhel7_minion.vm.synced_folder '.', '/vagrant', disabled: true
rhel7_minion.vm.network 'private_network',
:libvirt__network_name => 'primary_vagrant_private_net',
ip: '192.168.1.2',
:libvirt__netmask => '255.255.255.0',
:libvirt__forward_mode => 'route',
:libvirt__dhcp_enabled => true
end
config.vm.define "rhel5_minion" do |rhel5_minion|
rhel5_minion.vm.box = "uvsmtid/centos-5.5-minimal"
rhel5_minion.vm.synced_folder '.', '/vagrant', disabled: true
rhel5_minion.vm.network 'private_network',
:libvirt__network_name => 'secondary_vagrant_private_net',
ip: '192.168.2.3',
:libvirt__netmask => '255.255.255.0',
:libvirt__forward_mode => 'route',
:libvirt__dhcp_enabled => true
end
end