On Thu, Jan 15, 2004 at 03:18:50PM +0100, tom.van_driessche@xxxxxxxxxx wrote:
> I noticed that from release ethereal 0.10.0, the protocol 802.1q
> (virtual LAN) is supported.
It's been supported for a lot longer than that.
> I tried this out but I do not see any VLAN type (0x8100) nor VLAN tag in
> the ethernet frame.
You might be capturing on what might be called a "VLAN interface" - the
way a particular OS makes VLANs plug into the networking stack might,
for example, be to have a network device object for the physical
interface, which takes VLAN packets, strips off the VLAN header and
constructs an Ethernet header, and passes that packet to an internal
network device object for the VLAN, which then passes the packets onto
various higher-level protocol implementations.
> Lan switch which supports VLANs.
> Multiple devices connected exchanging messages with VLAN tags.
> Example : laptop with win2000. My VLAN tag is 10.
> When starting ethereal and start capturing the packets, I can select my
> virtual interface of my laptop supporting the VLAN.
That virtual interface is probably a "VLAN interface" of the sort
described above. Ethereal uses libpcap/WinPcap to capture packets; on
Windows, WinPcap's device driver connects to a network device object as
a higher-level protocol implementation, which, if Windows is an OS of
the type described above (as I suspect it is), means that the packets
handed to it are the packets with the constructed Ethernet header.
You would have to capture not on the virtual interface for the VLAN, but
on the interface corresponding to the physical network device, if
possible.
