Autodiscovery and a Virtual Machine

Hi All,
I have a program which uses autodiscovery.
It runs great on the 5 “Real” machines I have it on - however - the one virtual machine ( Proxmox ) it is really flacky on.

When you run the software on the VM it will show up on the other REAL machines members lists.
The software on the VM will always see all the other REAL machines.

If you close and run the software on a REAL machine (Mac or PC) the VM will not appear in that REAL machine member list even though that real machine still appears on the VM member list and can be sent messages AND the VM still appears on the other 4 REAL machines and can be sent messages.

If you then close and run the VM software the VM machine will appear on all the REAL machines members lists

In Short - The Virtual machine can see out and the Real machines can see in when they first start but when they leave the group and then return the Virtual machine isn’t there. In order to get the Real machine to see the VM you have to stop/start the VM software.

I have tried the number of RouterHops from 0 to 256 and I always get the same results.
It isn’t timing as I can issue an UpdateMemberList and wait minutes without the VM appearing on the list.

All the machines are on the one network and when I remote desktop to the VM the gatway and subnet mask are correct.

Four of the machines are WIndows Boxes XP / 7 , there is 1 mac, the VM is a XP windows box as well.

I know it is a very specific problem but has anyone else experienced any networking issues when working with VIrtual Machines?

Any thoughts, recommendations will be tested as I have exhausted my imagination.


@damon pillinger

what virtual machine software are you running? virtual box? vmware? hyper-v? etc?

what is the host machine (the machine where the virtual machine software runs)? mac? win? linux? and what version of it?

there can be interesting networking based on the combination of the two questions above.


HI Scott,

Proxmox is the virtual machine software and it runs in Linux.
Proxmox Version 3.2-4

Unsure as to which version of Linux as it is installed as part of Proxmox, however “uname -o” returns GNU/Linux


@damon pillinger I am not sure about ProxMox as I have never heard of it. I am sorry I can’t help further.

have you got the network card in bridged mode?

i’ve not used proxMox, but id suspect its set in NAT mode or similar.

Proxmox uses KVM or OpenVZ. Do you have a network adapter bridged to the VM that can access the same network? If not - you aren’t going to see it.

HI Scott,

If you are in Virtual Machine you should give ProxMox a go. IT is significantly better then the others in my opinion.



Hi Phill and Russ,
Yes the Proxmox machine is fine on the network as are the virtual machines within it. They all have access to the network and even back themselves up each night with EaseUS to a network drive.

The problem only seems to be with AutoDiscovery and a virtual machine.

I will do some more investigation.



Do you know off hand if other UDP based protocols are working off hand? If I recall AutoDiscovery is a UDP broadcast. Assuming you are correct and the VM’s are bridged correctly; The most likely scenario is the Proxmox iptables are not forwarding the UDP packets.

Something like should help you identify if its a network/UDP issue or a Xojo one.

Also, keep in mind that UDP packet delivery is not guaranteed. If you need that, you should be using TCP.