ad3y
Joined: 09 Feb 2007
Posts: 2
Helped: 2
|
 09 Feb 2007 13:23 Re: Vlan Tag |
|
|
|
Hi,
Try:-
h t t p://standards.ieee.org/getieee802/802.1.html
for the 802.1.q Standard, it is available in PDF format.
You are correct, 4 bytes are inserted into the ethernet frame between the source address and the type/length fields.
The first two bytes are a Tag Protocol Identifier, for 802.1q it is always 0x8100.
The next bytes are broken up as follows:-
Priority field: 3 bits - Used for traffic prioritization
Canonical Format Indicator (CFI) - 1 bit, 0 = MAC Address is in Canonical format, 1 = MAC Address is in Non Canonical format
VLAN ID (VID) - 12 bits, 0 is used to indicate frame is not part of a specific VLAN but has priority information, 1 - 4095 specify a VLAN that the frame is a member of.
Hope this helps,
Regards,
Adrian Hall.
|
|
