[PVE-User] Simulate disconnected network cable

Hart, Brian R. brianhart at ou.edu
Mon May 7 16:58:46 CEST 2012

One way I have done what you are looking for, though it is probably not their recommended way, is I've just deleted the bridged interface for the vm

If you do a 'brctl show' at the console on your proxmox box you'll see your bridged interfaces that list the bridge, the physical interface in the bridge, and the VM

They are listed as tap(VMID)I(Int#)

So for example, on vmbr0, on VM #107, net0, you might see a device listed in the bridge as: tap107i0

A command of brctl delif vmbr0 tap107i0 would remove the tap interface.  This would leave the NIC listed in your VM but not connected to the bridge and therefore not actually connected to your network.  Its not EXACTLY the same as VirtualBox there, but if you're wanting the NICs active and listed in your VM but not actually on the network this should accomplish what you're looking for.

There might be a better way, but this has worked for me in the past.

HTH --

Brian Hart

From: Jean Rousseau Franco <jfranco at maila.com.br<mailto:jfranco at maila.com.br>>
Date: Monday, May 7, 2012 7:45 AM
To: Mark Ehle <markehle at gmail.com<mailto:markehle at gmail.com>>
Cc: "pve-user at pve.proxmox.com<mailto:pve-user at pve.proxmox.com>" <pve-user at pve.proxmox.com<mailto:pve-user at pve.proxmox.com>>
Subject: Re: [PVE-User] Simulate disconnected network cable

Just for the clarification, CARP is part of the *BSD.

For the problem reported, for now you can simply use if-up/if-down or enable/disable the interface, since you´ll still have access to the machine via the web.

Best Regards,

2012/5/7 Mark Ehle <markehle at gmail.com<mailto:markehle at gmail.com>>
Thanks, Vassilis - however, I am not looking to have the VM automatically take over for the hardware firewall at this point. Like I said, in Virtualbox on the network settings page of the VM settings, there is a checkbox to "unplug" the virtual network cable to a virtual interface. Is there a way to do that with Proxmox?


On Mon, May 7, 2012 at 3:59 AM, Vassilis V. <Bigraccoon at gmx.net<mailto:Bigraccoon at gmx.net>> wrote:

Mark Ehle wrote on 06.05.2012 19:37:
> When I make changes to the
> physical machine I would like to update the config on the virtual
> machine, too, however, I can't bring the firewall VM up on the network
> because there is already a real machine on the network with the same IP
> addresses in use. Is there a way around this?

Hello Mark,

if I understand your question correctly, I think the CARP feature in
fsense is what you are looking for.


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