[Winpcap-users] use of winpcap with PLC net

Guy Harris guy at alum.mit.edu
Fri Jan 25 22:19:30 GMT 2008

Jean-Luc Pamart wrote:

> So I have for each PC  a INT51X device (ETH <->PLC)
> My PLC modem (a french brand OLITEC CPL400) is plugged into my home 
> wires and noting else (the eth connections are useless)
> It's pretty simple and it works fine !!!

OK, so the modem plugs into your phone line on its Internet side and 
directly into your home power wires on its LAN side (as well as having a 
WLAN antenna as well), and the PC's have Ethernet adapters plugged into 
Ethernet <-> HomePlug bridges, along the lines of the picture at


> Before that, I ask to my brand if my CPL/ETH can be put into promiscuous 
> mode. They don't give me a direct answer, they say that the
> devices are absolutely "transparent" ... that means I suppose : all the 
> traffic in the power lines are pushed to the ETH part.
> On one hand I a not sure of their answer

I wouldn't be sure of it either.  Perhaps the person you asked isn't 
technically knowledgable enough to understand what you were talking about?

> and on the other hand : when 
> you install the device, you don't have to configure something :
> you put the device into the socket and it's ok. And you can change the 
> devices between PC... So, if the PLC devices must filter the ethernet
> packets how they can do ?

Pass all broadcast and multicast traffic from the HomePlug network to 
the Ethernet, and:

	when they start up, pass all unicast traffic from the HomePlug network 
to the Ethernet;

	when they see a packet on the Ethernet, remember the source address, 
and pass to the Ethernet only unicast traffic that's sent to that address.

(That's called "MAC address learning".  I think most if not all Ethernet 
switches work that way.)

> So, if I can resume the directions :
> - my devices CPL (with INT51X) must to put in promiscuous mode and I 
> haven't made this operation

That might be the problem.

> - it's a problem of my 2 ethernets devices (one Linux, one Windows) they 
> says they go to the promiscuous mode and it's false

It's *possible* that might be the problem, but I think it's unlikely.

> => i will try with USB/CPL in windows

That might be worth trying.  With a USB adapter, there might be commands 
for the "Communications and CDC control" USB device class to put the 
adapter into promiscuous mode, and that might cause the adapter to 
capture all traffic on your power wires.

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