Comment on I need help with networking for VirtualBox guests running on Windows hosts.
maxy@piefed.social 1 week ago
Sounds like a networking exercise on its own.
Do the attempted pings show up on the wire? (Switch LEDs, network card activity light.)
Does broadcast work? (Watch if it is received with tcpdump -n on both Linux VMs, and Wireshark on the Windows hosts, while doing ping -b 10.0.0.255. Or trigger a broadcast ARP by ping-ing a non-existing IP in the same network. Those should go through all bridge and switch devices, independent of IPs and routing setup.)
I think you need four distinct MAC addresses for this setup, are they all different?
The network card/driver is filtering received unicast by MAC. I’m sure something should set up the filters correctly, but maybe it went wrong, or there is a bug in the driver. Wireshark on Windows should be able to enable promiscuous mode, which disables the filter.
Side note: I don’t think you need a crossover cable. Auto-crossover should just work these days.
At work I map a USB Ethernet device into my Linux VM when I do anything networking, exactly to avoid those kind of “is it Windows?” questions. Also, I can then check the Ethernet link at the lowest level using Linux tools like ip link or mii-tool or ethtool.
I’m using VMWare for this, which I cannot recommend any more. (It used to be good for this, but gut much worse in recent years.) I think vanilla VirtualBox doesn’t allow to map USB devices.
rtxn@lemmy.world 1 week ago
We have a winner!
The classroom computers were mass-deployed using Clonezilla, from a disk image that already had the VM pre-configured. As a result, every VM had the same MAC address. Bridged networking put both hosts and both VMs in the same broadcast domain, which caused collisions in the ARP tables. I randomized the MAC address of one VM and everything suddenly started working.
It’s never been an issue since we’ve never needed to use anything other than the default NAT adapter.
maxy@piefed.social 1 week ago
Thanks for the follow-up. Of course you would have some kind of mass-deployment, it didn’t think of that. I thought you’d maybe copy the Windows MAC to Linux, but… then you’d remember doing that.
Next up, they will also all have the same ssh host key ;-) (Which may be an advantage actually, but still confusing.) Those are the kind of problems cloud-init is solving, I guess.