VirtualBox host-only adapter keeps getting set to an invalid configuration, which breaks multicast.

[Fishscene]

Greetings!

OS: Windows 10 Pro x64 VirtualBox: 6.1.8r137981(Qt5.6.2)

The "VirtualBox Host-Only Network" adapter in Windows keeps getting set to an invalid state. When virtualbox is first installed, it populates the IPv4 IP address and DNS server. I also have to manually set the "Automatic Metric" to something like 800 as leaving it set to automatic breaks Multicast packets.

Every so often, I'll find I can't join a Multicast stream. Checking the settings in the "VirtualBox host-only network" adapter reveals:

• IP address/Subnet/Gateway are still set to manual, but are blank.
• DNS server is set to manual, and is completely blank
• Automatic Metric is set to automatic.

If I set the metric back to 800 and click ok, I get a message saying the IP address needs to be specified.

I have absolutely no idea what keeps changing the network properties for this adapter and setting it to an invalid state.

[Fishscene]

The program I use to listen in on multicast may be a factor here. I use VLC.

I found this post about VLC behavior when listening for Multicast packets: ​https://forum.videolan.org/viewtopic.php?t=78872 Specifically "The VLC player, as I have found, uses first ip address in the stack. Hence, we must push up the appropriate ip to high position by change its metric to lower value."

If the host-only adapter is somehow in the stack above the physical network adapter(even if it's the same metric), VLC may be defaulting to the host-only adapter.

[Fishscene]

It appears that at some point in the past, I had created a 2nd host-only network, and it was configured as: IPv4 Address: 0.0.0.0 IPv4 Network Mask: 0.0.0.0

The settings for this were stored somewhere in a vbox config file and thus persisted after uninstalling/re-installing Vbox.

Uninstall/Re-install Vbox would create 1 host-only adapter. After launching Vbox, the 2nd host-only adapter would be created. This was the adapter that I would manually set the administrative distance for and kept getting overwritten (by vbox configuration file upon launch).

I went to File > Host Network Manager and deleted the 2nd Host-only adapter (the option to delete it in Windows was grayed out).

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I will point out that after deleting the adapter, I was curious if vbox would let me create the invalid adapter again with the same settings. It does not. I'm wondering if I somehow created this adapter a few versions ago and it just carried over as vbox was upgraded. My specific scenario appears to be impossible to recreate. Well done vbox team. Well done. :)

I also want to give a shoutout to klaus-vb on IRC for working with me on this.

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For now, I'm considering this resolved. Error due to an old and incorrect configuration for host adapters.

[Fishscene]

Depicts bad host-only adapter settings that as of this Vbox version, is impossible to create. This was leftover from an older forgotten configuration.

[Fishscene]

Fresh reboot, multicast not working for VLC (left). After setting manual metric to 800, then back to automatic, I'm still receiving Multicast packets (right)

[Fishscene]

I have made no changes since the last post - other than to shut down my computer last night and turn it on again this morning. Multicast appears to still be working perfectly (Automatic metric is ticked).