In our testing about 2 years ago our juniper bng wouldn't handle 0x88a8 as
the outer tag when doing the auto conf demux stuff.
On Thursday, October 9, 2014, Nathan Ward <nznog(a)daork.net> wrote:
On 9 October 2014 at 1:09:42 pm, Brent Marquis (brent.marquis(a)chorus.co.nz
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
been updated in 2005 for CFI to be DEI:
Drop eligible indicator (DEI): a 1-bit field. (formerly CFI[note 1](
May be used separately or in conjunction with PCP to indicate frames
eligible to be dropped in the presence of congestion.(
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.