promiscuous mode disables itself

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promiscuous mode disables itself

Postby Joe55 » 28. Jul 2021, 20:43

I'm using a vm running server 2012 on a windows 10 host. Several networks are used; however one network is bridged to the physical adapter on my computer. I've set promiscuous mode to Allow All. It works however; if the device connected to the physical ethernet port is disconnected and reconnected (or power cycles) I can't connect to the physical device.

I can restore communications if I go into the machine settings and change the virtual network adapter (bridged to my physical adapter) promiscuous mode setting to 'deny', press 'ok' and close then go back into the settings and change it back to 'Allow all'.

It seems as though promiscuous mode auto disables itself if the physical cable is disconnected, but fails to update the setting. Is there a way to make it stay enabled?

Thanks, Joe
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Re: promiscuous mode disables itself

Postby scottgus1 » 28. Jul 2021, 20:51

While I can't speak on the Promiscuous Mode questions, Bridged is known to not work if the physical adapter being Bridged to is not "up", that is, not cable-connected to another device so the lights on the adapter are blinking. (The other device does not have to be connected to a valid network, there just needs to be a device there so the blinkenlichten are blinken.)

I would get a small switch and small cable, connect the PC's adapter to the switch via the cable, then duct-tape the dickens out of the ends of the cable so someone has to at least say, why are these taped? Then they will see the little sign you put on the cable saying, "Unplug this at your peril!" With the switch always connected to the PC's adapter, the adapter will stay "up", and Bridged won't stop working. Connect the network device being used to the switch. Throughput shouldn't suffer.
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Re: promiscuous mode disables itself

Postby Joe55 » 28. Jul 2021, 21:13

scottgus1, Thanks for the quick reply. Let me add some details.

I'm only using one VM on the machine, so if communications is broken while physical device is down, that's fine. In my case its a training environment, so the physical device is powered off frequently by students.

Side note, I don't think I ran into this issue on desktop PC's in my last class but have the issue this week on laptops. I'll have to test next week when I get back in town to be sure.
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