I'm stuck with choosing an IPv6 prefix for NAT Network

[Paddy Landau]

VirtualBox doesn’t support IPv6 by default, but it can be made to do so. I need it for some testing in my guest machine.

(I should probably state that my host uses IPv6 — I can see it on What Is My IP Address, among other places.)

To enable IPv6 in VirtualBox, I’m following these instructions to create a NAT Network in VirtualBox, but I’m stuck where I have to enter an IPv6 Prefix.

NAT Network IPv6 Prefix.png (24.98 KiB) Viewed 3537 times

I have no clue how to choose an IPv6 prefix. I’ve tried various ideas that I’ve found on the internet, but as none of them directly addressed the issue, and I don’t understand what it means, unsurprisingly I’ve not managed to make any of them work!

How do I work out what I’m supposed to put in there, please? (All that I know is that it’s supposed to be a /64 prefix, but I don’t even know what that means. )

I was advised to use

ip a | grep prefix

to find the right value. The command showed two different /64 values, but unfortunately neither of them worked.

Alternatively, if there's a better way to enable IPv6 in VirtualBox than using a NAT Network, that also would be great.

Host: Ubuntu 22.04
Guest: Ubuntu 24.04
VirtualBox version: 7.0.24 r167081 (Qt5.15.3)

Thank you

[multiOS]

The infrmation you linked to is not correct for for the VirtualBox version you are using (7.0.24), which does support IPv6.

Try searching the VirtualBox User Manual (pdf) for references to IPv6 instead of following an out of date (14 month old) forum post.

[Paddy Landau]

The infrmation you linked to is not correct for for the VirtualBox version you are using (7.0.24), which does support IPv6.

Thank you. I didn't even realise that there had been an update to 7.1 — for some reason, it wasn't offered as an update!

I have updated to 7.1.6, but unfortunately, I'm having problems with it (in a Windows guest, the menu doesn't show on full-screen; in an Ubuntu guest, the VM aborts on startup; in the VM settings, some settings are disabled). I'll create a new post to address those problems, before I continue with this one.

I do have a related question, though. The user manual doesn't appear to have a search bar. Is that correct, or am I missing something? EDIT: I found another user manual that seems to be better.

[multiOS]

I tend to use the PDF which is provided with the VirtualBox installer, so normally search that in a PDF Reader.

You won't have been prompted to upgrade to 7.1 because it's a full version upgrade with some significant differences and Version 7.0 is still supported and receiving regular updates. Many users prefer not to be 'nagged' jump to a new version upgrade until the 'early adopters' have helped to identify and report the problems! That said, a significant number of issues have been discovered and resolved since the release of 7.1.6 in /January (and to some extent 7.0.24) but, until 7.0.26/7.1.8 are released (expected soon), the fixes are only available in the 'Test Build' downloads available from https://www.virtualbox.org/wiki/Testbuilds

[Paddy Landau]

I tend to use the PDF which is provided with the VirtualBox installer, so normally search that in a PDF Reader.

Thanks for the idea. I have no idea where to find the PDF, so I'll use the online help (which, I would hope, is the most up-to-date).

You won't have been prompted to upgrade to 7.1 because…

That makes sense. I see that the VB Settings have an option to be notified of upgrades, so even though my system is set to auto-update, I've turned on that option.

… the fixes are only available in the 'Test Build' downloads available from https://www.virtualbox.org/wiki/Testbuilds

Thank you. Perhaps I'll wait for them to move out of test and into production.

[Paddy Landau]

Thanks for your help.

I found the solution to my crashing VM, so I'm able to use VirtualBox 7.1.6.

I'm pleased to say that this version supports IPv6 out of the box, no special settings required, so my problem is solved!

[multiOS]

That's great. Glad that's solved for you.