Ethereal-users: Re: [ethereal-users] Sniffing 802.1Q connections

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From: Guy Harris <gharris@xxxxxxxxxxxx>
Date: Mon, 3 Jul 2000 17:46:20 -0700
On Mon, Jul 03, 2000 at 04:22:57PM -0500, Brian Capouch wrote:
> This is more an informational question unless the behavior I'm about to
> describe is identified by a cheese as being a bug.
> 
> Just for s & g, I brought up a couple of Linux boxes using VLANS.  I
> stuck ethereal on the connection, and it nicely decoded the VLAN tag,
> FOR ONE SIDE.
> 
> It identified and displayed the VLAN stuff correctly for the side of the
> connection that was on the host doing the sniffing, but couldn't see it
> (i.e. no 802.1Q stuff anywhere in the packet info) for the other side.

What *did* it display for the other side?

Could you send us a capture file that shows this behavior?

Ethereal should dissect a packet as an 802.1q packet iff the packet's
Ethernet type field has the value 0x8100; did the packets on the other
side of the connection have that Ethernet type?  If not, what did their
Ethernet header contain?