Linux bridge method steps to bridge two VirtualBox virtual networks

So how does the switch register the Mac address? In other words, where can I see which Mac a network card of a virtual machine is registered to?

Please see "Virtual Machine -> Settings -> Network":

Each time you activate a network card, expand the Advanced below to see the registered Mac address of the network card.

It is now clear why the above experiment did not work. When H1 pings H2, the ARP request can be broadcast to H2 via the Linux Bridge. In the ARP broadcast received by H2, the source MAC is naturally the MAC address of H1. When H2 replies to the ARP Reply, the target MAC is the MAC address of H1. However, the MAC address of H1 is not registered in the virtual switch of intnet2, so the switch of intnet2 will not forward this frame. So naturally it doesn’t make sense!

Okay, next, I will open up its Ren and Du meridians and make them unobstructed! It's time to show the How.

Only three steps are required:

• Register the MAC address of H1 on intnet to the intnet2 network card enp0s10 of Linux Bridge.
• Register the MAC address of H2 on intnet2 to the intnet network card enp0s9 of Linux Bridge.
• After the Linux Bridge host is up, use the ifconfig command to change the MAC addresses of the enp0s9 and enp0s10 network cards to other ones.

Let me show you how to do it.

We can see that there seems to be no option to specify a MAC address on the network card configuration interface, only a button to randomly generate a MAC:

what to do?

Use the command line!

We use the VBoxManage command to specify the MAC address of a specific network card as follows:

zhaoyadeMacBook-Pro:~ $ VBoxManage modifyvm "ubuntu new" --macaddress4 0800279ff0e6
zhaoyadeMacBook-Pro:~ $ VBoxManage modifyvm "ubuntu new" --macaddress3 080027bb3d67

The 0800279ff0e6 in the above is the MAC address of H1 enp0s9, and 080027bb3d67 is the MAC address of H2 enp0s9. From their network configuration interface, we can see:

OK, now start the Linux Bridge machine and complete the third step. This step is needed to prevent address conflicts from poisoning the Bridge's forwarding table:

• 0800279ff0e6 can be learned from H1's intnet.
• 0800279ff0e6 is configured on its own enp0s10.

Are you confused? Therefore, the MAC addresses of the two network cards enp0s9 and enp0s10 of the Linux Bridge must be changed to other ones. The VirtualBox Internal Network switch is unaware of this modification (only activating a new network card or re-registering a new MAC will change the forwarding table, that is, clicking the small button or executing the VBoxManage command to change the MAC address), so it does not affect its forwarding table.

Ok, let's do it:

ifconfig enp0s9 hw ether 08:00:27:bb:3d:68
ifconfig enp0s10 hw ether 08:00:27:9f:f0:e7

OK, all steps are done, let's test:

brctl addbr br0;
brctl addif br0 enp0s9;
brctl addif br0 enp0s10;
ifconfig br0 up;

Ping again?

Isn't this the solution...

In fact, the bridging in HostOnly mode is similar to that in Intenal Network, and has the same problem and solution.

I don't know whether this problem of not being able to bridge two networks is intentional by VirtualBox or it is really an implementation defect, but I really encountered this requirement in actual work, so in my personal opinion, it is a defect! This is obviously inferior to VMWare's LAN Segment.

Or does VirtualBox only have this problem on Mac OS? Is it fine on Windows? I can’t say for sure. It’s been almost two years since I left the Windows platform.

This problem was solved in almost a day.

At first, I thought it was a problem with my brctl configuration. How could such an obvious operation not work? I was puzzled. I used HostOnly to do the experiment, and then I found through packet capture that the return packet of H1 was directly returned to the vboxnet1 network card of the Mac OS host, and vboxnet1 did not forward the packet to the Linux Bridge. I first suspected that it was a BUG in VirtualBox. After restarting the system to no avail, I roughly guessed what it meant. As for the term "registered switch" , it's just my own guess. Anyway, it's pretty close, and I obviously solved it following this problem.

I haven't encountered this kind of problem for a long time, but I still like and am good at solving this kind of difficult problems. I am not very good at writing tutorials on conventional knowledge, but for this kind of strange problem that people don't encounter very often, I have my own magic medicine here.

Before I found the answer, I Googled for a long time, looking for things corresponding to LAN Segment on VirtualBox, and looking for the difference between Internal Network and LAN Segment. I even wanted to find a Virtual Switch on Mac OS to create a virtual and real Ethernet myself... If I really can't find it, I can only DIY one.

Fortunately, before I started this extremely unrealistic big scene, I suddenly thought of the solution to the problem described in this article. Thank God~

The above is the full content of this article. I hope it will be helpful for everyone’s study. I also hope that everyone will support 123WORDPRESS.COM.

brctl addbr br0;
brctl addif br0 enp0s9;
brctl addif br0 enp0s10;
ifconfig br0 up;

ifconfig enp0s9 40.40.40.201/24

ifconfig enp0s9 40.40.40.100/24