Oops, copy and passed the wrong link, but the right quote. http://en.wikipedia.org/wiki/IEEE_802.1Q 802.1Q does show DEI, rather than CFI and appears to be a 2005 change to 802.1q standard. 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) Thanks, Brent Brent Marquis | Layer 2 Network Specialist [cid:image001.png(a)01CFE3C8.F7184140] Chorus | T : +6448964169 | M :+64272290923 From: Nathan Ward [mailto:nznog(a)daork.net] Sent: Thursday, 9 October 2014 1:26 p.m. To: Brent Marquis; Dave Mill; Don Stokes Cc: nznog(a)list.waikato.ac.nz Subject: Re: [nznog] UFB Upload Issues On 9 October 2014 at 1:09:42 pm, Brent Marquis (brent.marquis(a)chorus.co.nz(mailto:brent.marquis(a)chorus.co.nz))mailto:brent.marquis(a)chorus.co.nz(mailto:brent.marquis(a)chorus.co.nz)) wrote:
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:
http://en.wikipedia.org/wiki/IEEE_802.1ad
Drop eligible indicator (DEI): a 1-bit field. (formerly CFI[note 1](http://en.wikipedia.org/wiki/IEEE_802.1Q#cite_note-2)[2](http://en.wikipedia.org/wiki/IEEE_802.1Q#cite_note-3)) May be used separately or in conjunction with PCP to indicate frames eligible to be dropped in the presence of congestion.[3](http://en.wikipedia.org/wiki/IEEE_802.1Q#cite_note-4)
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 do this. -- Nathan Ward This communication, including any attachments, is confidential and may be legally privileged. If you are not the intended recipient, you should not read it - please contact me immediately, destroy it, and do not copy or use any part of this communication or disclose anything about it. Thank you. No confidentiality or privilege is waived or lost by any mis-transmission or error. Please note that this communication does not designate an information system for the purposes of the Electronic Transactions Act 2002.
