Multicast originating from different subnet does not reach Guest only when Ubuntu Host

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idmistir
Posts: 4
Joined: 7. Nov 2021, 23:47

Multicast originating from different subnet does not reach Guest only when Ubuntu Host

Post by idmistir »

Hello,

I have run into a very weird issue as partially explained on the title which I really hope you can help me with.

Basically, I am receiving status updates from various devices on the network in my VM. They use multicast on 224.0.0.50.
The devices are on a different subnet from the Host and the Guest (the host and the guest are on the same subnet), but everyone can communicate between each other just fine.
This works on Host Windows 10 but not on Host Ubuntu 18.04. Using Virtualbox 6.1.28. Tried 6.1.26 also.

The guest is using bridged networking.
On Windows it's using Intel PRO/1000 MT Desktop (82540EM). On the Ubuntu host I've tried them all with no luck.
On Windows promiscuous mode is set to Deny and greyed out, on the Ubuntu host I tried enabling it to Allow-All, no luck.

Both hosts receive the multicast packet (used wireshark on windows and tcpdump on linux to verify on both the hosts and the guests), but only on the Windows 10 host will it manage to be picked up by the Guest.
I'm attaching a screenshot from a packet capture from inside the Guest with Windows 10 as a host. These two packets are the expected behavior. On Ubuntu Host, only the first one (the direct reply) makes it all the way to the Guest. The multicast packet is lost.

Multicast packets originating from the same subnet are well-received.

Am I missing something, or is this a bug?
Attachments
Capture from the Guest while on Windows 10
Capture from the Guest while on Windows 10
vbox.png (8.7 KiB) Viewed 3350 times
idmistir
Posts: 4
Joined: 7. Nov 2021, 23:47

Re: Multicast originating from different subnet does not reach Guest only when Ubuntu Host

Post by idmistir »

Should I make a bug report instead?
scottgus1
Site Moderator
Posts: 20965
Joined: 30. Dec 2009, 20:14
Primary OS: MS Windows 10
VBox Version: PUEL
Guest OSses: Windows, Linux

Re: Multicast originating from different subnet does not reach Guest only when Ubuntu Host

Post by scottgus1 »

We've seen this one, but so far no one knowns how to troubleshoot it. Multicast isn't something I have any experience with.
idmistir
Posts: 4
Joined: 7. Nov 2021, 23:47

Re: Multicast originating from different subnet does not reach Guest only when Ubuntu Host

Post by idmistir »

Thank you for your reply. I feel like it's a driver issue. I'll probably submit a bug report if I don't figure it out myself soon or if there's not any further insight.
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