SixConf is a powerful tool for learning or teaching IPv6. It is not Open Source, but it is free app for Windows. I wrote this to help my students when I was teaching IPv6. It is referenced in several places in this website. It’s OK to download and share it with students or co-workers – please don’t re-post this yourself – post a link to this training instead.
SixConf is provided with no support, but if you have feedback you can send it to firstname.lastname@example.org. It was written in C#.Net. The source code is not available.
See the User Guide for full details, but here is a screenshot of the main window to give you an idea of how it works. You can view all IPv6 and IPv4 addresses, including unicast, multicast, etc. You can add new addresses. It supports all network interfaces on your PC.