On Thu, Apr 03, 2003 at 09:21:27AM +0200, Elias Todorovich wrote:
> I'm implementing QoS and now I'm trying to test if in my subnetwork a
> sender and a receiver are sending the 802.1p tag. How should I see this
> tag with Ethereal?
If you're capturing on the *raw* Ethernet, so that the tag header isn't
stripped off before the packet is supplied to whatever capture mechanism
is used (for example, if a system using VLAN tagging has separate
network interfaces for the raw Ethernet and for VLANs, if you capture on
one of the VLAN devices the tag header might not be seen; I don't know
whether that would happen if you're using priority tagging but not
VLANs, nor do I know what interfaces would strip the headers and which
wouldn't, nor do I know whether interfaces that don't strip the headers
would be available on your system, so I can't help you with that), then
the packet should have, when displayed by Ethereal:
an "Ethernet II" header, with destination and source MAC
addresses, and a type field with "802.1Q Virtual LAN (0x8100)"
as the value;
an "802.1q Virtual LAN" header, with a 16-bit Priority/CFI/ID
field showing those values as bitfields, and a type field with
the actual packet type;
the payload appropriate for the actual packet type (IP, ARP,
IPX, IPv6, etc.).
If you're using prorities but not VLANs, the ID field would be 0 (null
VLAN ID).