Chapter 6
| Port Connections
DAC Connections
– 48 –
4. As a connection is made, check the Link LED on the switch to be sure that the
connection is valid.
DAC Connections
Direct Attach Cable (DAC) is a method of connecting SFP+/QSFP+ interfaces
without using optics and fiber cable. A fixed length of twinax copper cable is
terminated at each end with physically-compliant SFP+/QSFP+ transceivers that do
not include all their normal electronic and optical components. The result is a low
cost, low-latency, 10/40G Ethernet solution for short distances, ideal for
connections within the data center.
A 40G DAC connection is also known as twinax copper or 10GBASE-CR4. DAC
copper cables are available in pre-terminated fixed lengths up to 7 m (22.9 ft).
When operating in four-lane mode, a 40G QSFP+ port can also connect to four 10G
SFP+ ports using a DAC breakout cable.
Making DAC
Connections
1. Plug the SFP+ transceiver connector on one end of a twinax copper cable
segment into an SFP+ slot on the link device.
Figure 28: Making DAC Connections
Table 15: Maximum 10GBASE-CR4 10 Gigabit Ethernet Cable Lengths
Cable Type Cable Lengths Connector
Pre-terminated Direct Attach Cable
(DAC)—(twinax copper cable)
1 m (3.28 ft)
2 m (6.56 ft)
3 m (9.8 ft)
5 m (16.4 ft)
7 m (22.9 ft)
QSFP+
QSFP+ Transceiver Slot QSFP+ DAC Cable
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