Oops, copy and passed the wrong link, but the right quote.
802.1Q does show DEI, rather than CFI and appears to be a 2005 change to 802.1q
Sorry for the confusion, but it would seem from the wiki information that Don would have
been right if we were in 2004 (and/or possibly for anyone running software on switches
from pre-2005 amendment to 802.1Q)
Brent Marquis | Layer 2 Network Specialist
[cid:image001.png@01CFE3C8.F7184140] Chorus | T : +6448964169 | M :+64272290923
From: Nathan Ward [mailto:email@example.com]
Sent: Thursday, 9 October 2014 1:26 p.m.
To: Brent Marquis; Dave Mill; Don Stokes
Subject: Re: [nznog] UFB Upload Issues
On 9 October 2014 at 1:09:42 pm, Brent Marquis
Sorry for the quick reply to myself!
It actually seems like Don might not be 100% correct.
I don’t have IEEE access to get the .1q standard… But Wikipedia suggests it has been
updated in 2005 for CFI to be DEI:
Drop eligible indicator (DEI): a 1-bit field. (formerly CFI[note
May be used separately or in conjunction with PCP to indicate frames eligible to be
dropped in the presence of
With the note suggesting – “IEEE 802.1Q-2005 clause 9.6”
If it’s on Wikipedia, it must be true…. Right? J
The quote above is from the 802.1q page. If you read the page you link to, the 802.1ad
page, you get:
In IEEE 802.1ad the CFI is replaced by a Drop Eligibility Indicator (DEI), increasing the
functionality of the PCP field.
Key bit is “802.1ad”, not 802.1q. Using 0x88a8 vs 0x8100/0x9100 is signalling that you’re
using 802.1ad vs. stacked 802.1q, so should set this bit appropriate to the tag type.
I’m with Don on this one - the frame type bits signal how to interpret the following bits,
you can’t just swap them around.
People should really just use 0x88a8 - those who aren’t, can I ask why not? Is it because
you’re trying to tunnel it over a switch that doesn’t support 802.1ad or something? I’m
not saying it’s wrong, I’m interested in understanding the situations in which you might
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