I would like to connect and setup two of GS316EPP, I also have QSFPTEK 10G SFP+ DAC Cable,

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Underain wrote:
... connect two GS316EPP. I have QSFPTEK 10G SFP+ DAC Cable, 0.5m (2ft) Passive Direct Attach Copper Twinax Cable, 10Gb SFP+ to SFP+.

In general, a DAC (or two copper or fiber modules with the appropriate link media) establishing a plug-and-play connection between two SFP or SFP+ ports.

While in the first view, a "passive cable" sounds like a possible approach, the cable respectively the two connector modules at the two ends, does indicate much higher data rates (only!) than the GbE (technically operating at maximum of 1.25 Gb/s on the SFP port) does handle.

SFP and SFP+ transceivers are virtually identical in size and appearance. The primary difference is that SFP+ is an updated version that supports higher speeds up to 10G/s. The difference in data rate also accounts for a difference in transmission distance - SFP based on SFF INF-8074i typically has a longer transmission distance. SFP+ specifications are based on SFF-8431. In terms of SFP vs SFP+ compatibility, SFP+ ports often accept SFP optics but at a reduced speed of 1 Gb/s (exact PHY rate 1.25 Gb/s).

Be aware, however, that you cannot plug an SFP+ transceiver into an SFP port because SFP+ does not support speeds less than 6 Gb/s.

Sometimes, even a successful established link is indicated to the switch and the link and the switch does turn the LEDs on, while it's establising a much faster link than the switch - but no data does and can flow.

The 1.25G SFP Cable, SFP DAC, 1GBASE-CU Passive Direct Attach Copper Twinax Cable are still in the market, but are less commonly available then the SFP+ 10GBASE-CU passive cables. 

Commercially spoken, prices for some short reach fiber modules (and matching short fiber patch cables) have reached that low prices in the markets, so the price advantage of DAC became mostly obsolete.

Hope this clears up the confusion here. 

Regards,

-Kurt.