Internal networking with a Linux and a Windows guest

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On a physical machine running Windows 10 Pro with the latest version of Virtualbox installed, I have a fully functional Linux guest with a working Internet connection via a Bridged Networking configuration in Vbox. Additionally, I have a second adapter configured in this guest attached to what , I believe, is a Virtualbox internal network. I also have a Windows guest (Win 10 Pro) configured with an adapter attached to the same Virtualbox internal network. There seems to be some sort of communication capability between these two guests on this internal network because I can ping each from the other one. However, what I would like to do is see the Windows guest make Internect connectiviity via the connection, just as the Linux guest already has. However, this last step seems to elude my techincal abilities.

Just for the sake of testing, I did drop the Windows firewall temporarily. Also, I did issue this command in the Linux guest: sysctl net.ipv4.ip_forward=1. It seems as though there must be another step, but I cannot understand what it should be or find more information for a clue. Any informed ideas would be welcome. Thanks.

[mpack]

Additionally, I have a second adapter configured in this guest attached to what , I believe, is a Virtualbox internal network.

That is rather vague. What exactly is the second NIC configured for? Do you mean it is configured for "Internal networking"?

Why didn't you just use bridged networking in the Windows 10 guest too? That way all guests (and the host) would be on a single network, the physical one. That would appear to be simpler than configuring guests with unusual network configurations. Why was this not suitable?

I also have a Windows guest (Win 10 Pro) configured with an adapter attached to the same Virtualbox internal network. ... what I would like ... the Windows guest make Internect connectiviity

Well, that isn't going to work, since it doesn't have an Internet connection. You would need to configure a gateway, and have gateway software of some kind running on the Linux PC (the other VM) to channel data to and from the other NIC. I'm not a Linux user so I can't tell you what software would work there. On a Windows PC I imagine you would configure Internet Connection Sharing, though I won't swear to that either since I've never needed it (all my PCs are on a single physical network as recommended above, connected to a common router).

[Perryg]

Internal is an isolation protocol. It was designed to *not allow LAN or internet access. You would need a pFsense guest in the internal network to provide routing and it will then be able to reach the Internet.

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mpack, hello. I do appreciate the reply.

> "That is rather vague."

It seems clear enough to me, but I can rephrase if you like. My second interface in the Linux guest is attached to the Virtualbox Internal Networking device configured with the GUI, yes. Currently, I am simply testing this configuration in order to understand what is necessary and what is capable with the VB Internal Networking; I am not assuming this is the desired end-game.

I am solving the technical requirements in steps so that I can be sure I fully understand each part before moving forward. Thus far I have achieved this much:

I have, as I mentioned earlier, a Linux guest with two network interfaces (actually three but one is disconnected for now). The first of these two interfaces is bridged to the host network and it has a fully functional Internet connection. Now, what I need is to figure out, quite separately mind you, how one is supposed to configure Internal Networking between a Linux and a Windows guest. The Virtualbox instructions in the online manual seem rather vague in this regard, in my opinion; and the various instructions I found so far by googling have significant differences or they apply to guest running only the same OS, such as both Linux or both Windows, but not mixed.

One point in particular for which I want clarification was made in the Virtualbox online guide:

"As a security measure, the Linux implementation of internal networking only allows VMs running under the same user ID to establish an internal network."

As I understand this point, it means that two or more guests, all running Linux, must have the same user ID. My question is whether it implies the same when one of the guests is Linux but the other is Windows. Alternatively, can I completely ignore the statement whenever a Windows OS joins this Internal Network?

A second point for which I want clarification in relation to the Internal Networking is what sort of gateway should be configured on the interfaces? In general, where is the guide for configuring such settings on these interfaces? By this question, I do not mean how does one configure an adapter, as this much I already know, but what are example settings to be used for adapters in an Internal Networking, such as these:

IP address
subnet mask
default gateway
broadcast

I am not, obviously, a networking expert although I intend to become much more of one with Linux anyway as I work through this problem. I do not believe that this is an "unusual network configuration." Actually, it seems rather common and not terribly omplicated. Simply put, I want only one guest to provide an Internet connection to the other guests on a Virtualbox Internal Networking group. Right now I have one guest with two interfaces, one of which is a fully functional bridged connection to my LAN through the host; and the second interface should be connected to the Internal Networking group along with the other guests in the group. In order to accomplish this I "first" need to know what sort of proper settings these Internal Networking guests should have. Thanks.

[mpack]

> "That is rather vague."

It seems clear enough to me

I said that because you said you were using a particular network mode, you believe. It seemed to me that there was no need for speculation - you could just tell us straight what network mode you had used in the VM settings. Obviously, the quality of any reply you get will depend a lot on the quality of information provided.

As to whether a particular network task is unusual, take it from me: if it involves more than one Ethernet adapter in a PC then it is not the usual configuration. VMs don't change the rules in that regard.

Since it seems that your goal is to learn about internal networking, then I don't believe I have much more to offer on that subject.

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Internal is an isolation protocol. It was designed to *not allow LAN or internet access. You would need a pFsense guest in the internal network to provide routing and it will then be able to reach the Internet.

Actually, there is a simpler way, which I have now implemented and it works perfectly. One does not need to install pfsense or another such system. The routing magic is done by using Internet Connection Sharing from the bridged adapter to the one connected to the Internal Network on a separate subnet. Then any of the VMs on the internel network can access Internet when their adapters are properly configured to the same subnet. It works for both Linux and Windows guests in the Internal Network.