Twinax trivia check (was Re: Is there such a thing as a 10GBase-T SFP+ transciever)

Brian Loveland brian at
Mon Feb 3 04:04:51 UTC 2014

We've worked through the same issues with Brocade/Intel, although we found
that even though Brocade specs active only, our ICX switches don't reject
passive cables, although oddly the Intel branded passive cables show up as
UNSUPPORTED (but FCI and Molex ones from Digikey show up as the correct
length and correct type of cable).
If you do decide to go generic make sure you check the sizing.  Maybe
Brocade SFP+ drive is weak but using some 28 AWG 5M cables we've seen it
takes a lot of errors.  Switching to 26 AWG or 24 AWG solved the issue.  I
suspect Brocade requires active just from their storage background.

On Sun, Feb 2, 2014 at 5:49 PM, Murphy-Olson, Daniel E.
<dolson at>wrote:

> Most of the switch vendors have an "official" compatibility list, but I've
> found that generally the most common compatibility issue is active vs
> passive twinax.
> Brocade edge switches and nics are normally active only, which seems to
> come up a lot - because most short cables are passive unless they are
> brocade branded.  >5m is normally the cutoff for passive twinax.  Pretty
> much everything else I've encountered supports passive.
> For a while, the intel x520 nics, which are very common, didn't support
> active connections - but they have since released firmware that fixes this
> problem.
> Netapp's lower end gear doesn't support active twinax.
> ________________________________________
> From: Jeff Kell [jeff-kell at]
> Sent: Sunday, February 02, 2014 3:15 PM
> To: Bryan Tong; Jay Ashworth
> Subject: Re: Twinax trivia check (was Re: Is there such a thing as a
> 10GBase-T SFP+ transciever)
> On 2/2/2014 4:03 PM, Bryan Tong wrote:
> > These cables are most commonly known as "Direct Attach Copper SFP+"
> The big issue appears to be that these are not always "consistently
> functional" crossing vendor lines (sometimes product lines within the
> same vendor).  There does not appear to be any standardization in
> place.  Not sure how much of this is picky vendor software looking for
> "branded" marks in their transceivers (e.g., Cisco "service
> unsupported-transceiver") versus true incompatibilities.
> We have had issues in test cases crossing vendor lines (Cisco / Brocade
> / Dell / HP) with a "twinax" link that just simply won't work.  If
> anyone has a clear explanation or better understanding, I'm all ears.
> Personal experience comes from only a few testbed cases.
> Jeff

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