Re: VLAN Security

[sstefanov () ORBITEL BG (Stefan Stefanov)]

bugtraq () SIS ALPHAWEST COM AU wrote:
> To Bugtraq,
>
> We have recently conducted some testing into the security of the
> implementation of VLANs on a pair of Cisco Catalyst 2900 series
> switches and we feel that the results of this testing might be of some
> value to the readers.  Testing basically involved  injecting 802.1q
> frames with forged VLAN identifiers into the switch in an attempt to
> get the frame to jump VLANs.  A brief background is included below for
> those that might not be too familiar with VLANs.  Others should skip
> to the end for the results.

Interesting proposal, but I think it is more or less Cisco specific.
Here I have a BayStack 350T-24 running software revision 1.0.0.2.
According to the documentation the switch has the following feature that
can be configured on per Port basis:

Filter Tagged Frames: Allows you to set this port to filter (discard)
all received tagged packets.

I think all the ethernet switches should filter all tagged frames when a
port is not a trunk port. This way a machine that is connected to a non
trunked port, should not be able to send frames with 802.1q tags in it.

In your example the switch should have filtered the tagged frames.

--
Best Regards,

Stefan Stefanov
Orbitel Ltd.