PPPoE + Switch sniffing

Hello friends,

As a manager of my network, I am woried of security. Recently we
changed the HUB's for switch's in hope that we get more securitty.

In a few days ago, we have seeing another Access concentrator in our
network sending PADO's to the clients that wanted to connect.

This access concentrator have the same MAC address of one of my clients.

I would like to know what do you think that could be?
I've searched google for this, but I didn't found any attack baseed on
PPPoE + switch.
Could this other access concentrator be trying to give connection to
some of my clients just to sniff their connection?

Thanks,
Carlos.

--
http://users.urbi.com.br/carlos_oliv

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