Chapter 5
| Port Connections
DAC Connections
– 44 –
DAC Connections
Direct Attach Cable (DAC) is a method of connecting two 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, 10G/40G Ethernet solution for short distances, ideal for
connections within the data center.
A 10G DAC connection is also known as twinax copper or 10GBASE-CR. DAC copper
cables are available in pre-terminated lengths up to 10 m (32.8 ft).
For 40G DAC, or 40GBASE-CR4, copper cables are also available in pre-terminated
lengths up to 10 m (30 ft).
Making DAC
Connections
1. Plug the SFP+/QSFP+ transceiver connector on one end of a twinax copper
cable segment into an SFP+/QSFP+ slot on the link device.
Table 9: Maximum 10GBASE-CR 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)
SFP+
Table 10: Maximum 40GBASE-CR4 40 Gigabit Ethernet Cable Lengths
Cable Type Cable Lengths Connector
Pre-terminated Direct Attach Cable
(DAC) — (twinax copper cable)
Up to 10 M QSFP+
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