A server administrator is deploying a new high-performance computing server that must connect to a top-of-rack switch at 40 GbE. Both the server's network interface card and the switch have available QSFP+ ports. The distance between the server and the switch is less than 3 meters. Which of the following provides the most cost-effective and appropriate solution for this connection?
A QSFP+ Direct Attach Copper (DAC) cable.
Two SFP+ transceivers and a multimode fiber cable.
Two SFP transceivers and a Cat 6a twisted-pair cable.
Two QSFP+ transceivers and a single-mode fiber cable.
The correct answer is a QSFP+ Direct Attach Copper (DAC) cable. For short-distance connections within a server rack, such as the 3-meter link described, a 40 GbE QSFP+ DAC is the most cost-effective and power-efficient solution. It consists of a fixed twinax copper cable with QSFP+ connectors on both ends.
Using two SFP+ transceivers is incorrect because SFP+ is designed for 10 GbE speeds, not the required 40 GbE. While QSFP+ transceivers are correct for 40 GbE, using them with single-mode fiber is not appropriate or cost-effective for a 3-meter connection, as single-mode fiber is intended for long-distance transmissions, often several kilometers, and its transceivers are more expensive. SFP transceivers are incorrect as they are typically used for 1 GbE speeds, and Cat 6a cabling with RJ-45 connectors is not compatible with QSFP+ ports.