5-9
Chapter 5: Making Network Connections
4. As a connection is made, check the Link LED on the switch to be sure that the
connection is valid.
NOTE: Be sure to secure cables properly and route them away from the switch without
exceeding the minimum bending radius for fiber cables (typically a few inches). Use cable
ties to bunder cables together and secure coiled loops of excess cable. Do not let cables
hang free supporting their own weight or pull in any way that puts stress on the connectors.
5-6 DAC Connections
Direct Attach Cable (DAC) is a method of connecting two QSFP+ interfaces without
using optics and fiber cable. A fixed length of twinax copper cable is terminated at each
end with physically-compliant QSFP+ transceivers that do not include all their normal
electronic and optical components. The result is a low cost, low-latency, 40G Ethernet
solution for short distances, ideal for connections within the data center.
A 40G DAC connection is also known as twinax copper or 40GBASE-CR4. DAC copper
cables are available in pre-terminated lengths up to 7 m (22.9 ft).
Figure 5-5. Making a Connection to an QSFP+ Transceiver
QSFP+
Transceiver Port
QSFP+ Fiber
Optic Cable
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