Need help understanding differences between public and private networking and how that affects port forwarding

[micky...@gmail.com]

Hello,

Networking noob here. Nice to meet everyone!

I have created a Vagrantfile where I use a variable that allows me to switch between public or private networking types:

https://github.com/mhulse/vagrant-latmp/blob/382ca7463570f751a1f39d258cb4936c7b9640ba/Vagrantfile

I am not sure if I fully understand which network type is most optimal to use and when ...

• When would I want to use private over public?
  
• Which one would work best (or at all) with forwarded ports?
  
• What is the advantage to one over the other?
  

Here's my current understanding (could some one confirm/deny/correct my assumptions):

1. NAT port forwarding = "private_network"
• Connect, from host, using "localhost"
• Port forwarding works (why? because localhost is used by host machine and ports could collide?)
• Setting "auto_correct" will fix any port collisions between guest and host
2. Public Network (VirtualBox Bridged networking) = "public_network"
• You have to connect using IP address of box (DHCP or defined via config.vm.network.ip)
  
• Port forwarding does not work (why? is this because the machine handles this via Apache/Tomcat, etc, and using IP means no sharing by host machine so no ports would collide?)
  
• Setting "auto_correct" is not needed because port forwarding isn't needed (or is ignored by Vagrant when network type is "public"?)

So it sounds like, to clarify my thoughts/understanding further:

• Use "private_network" (Vagrant default) if you want to use "localhost" and use port forwarding to avoid port collisions between guest VM and host machine.
  
• Use "public_network" if you want to connect to VM using IP address; port forwarding is not required because VM uses it's own IP address so ports will not collide between guest VM and host machine.
  

Does that sound right?

One last question:

• If you use "private_network", and provide an IP, do you still have to worry about forwarded ports and collisions (assuming yes)?
  

Thanks so much for taking the time to read/help. Sorry if noob questions. Just trying to learn and become more aware of how things work. :)

[Mário Costa]

Vagrant uses virtual machine backends, such as Virtualbox, so its configurations map to the capabilities of the backend.

From a Google search the first result:

https://www.thomas-krenn.com/en/wiki/Network_Configuration_in_VirtualBox

Cheers

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[Micky Hulse]

Hi Mário, thanks so much for the quick reply and help, I really appreciate it!

On Tue, May 22, 2018 at 2:17 PM, Mário Costa
<mario.si...@gmail.com> wrote:
> Vagrant uses virtual machine backends, such as Virtualbox, so its
> configurations map to the capabilities of the backend.
> From a Google search the first result:
> https://www.thomas-krenn.com/en/wiki/Network_Configuration_in_VirtualBox

Reading now, thanks for the pointer!

[micky...@gmail.com]

For anyone else interested in this topic, I found a good blog article here:

https://blogs.oracle.com/scoter/networking-in-virtualbox-v2

I think I like the sound of "Port-Forwarding with NAT Networking"; I think this translates to Vagrant as "private_network" for "config.vm.network" and then specify your "forwarded_port"(s) via the config.vm.network setting.

I guess I'm just looking for a "one size fits all" solution.