N10-009 Question 100
Single answerForm factors: Small form-factor pluggable (SFP), Quad small form-factor pluggable (QSFP)A network administrator is upgrading the uplinks between a top-of-rack switch and a distribution switch in a data center. The existing top-of-rack switch has standard SFP ports currently used for 1 Gbps fiber uplinks, but the new design requires a single 40 Gbps uplink per rack without replacing the distribution switch. The distribution switch has available QSFP+ ports. Which solution best meets the requirement with the fewest physical connections?
- A
Install a QSFP+ transceiver on the distribution switch and use a matching 40 Gbps connection to a QSFP+ uplink port on the top-of-rack switch
- B
Install four SFP transceivers on the top-of-rack switch and bundle them into one native 40 Gbps link without any special support
- C
Replace the SFP transceivers on the top-of-rack switch with RJ45 copper modules to increase the uplink speed to 40 Gbps
- D
Use a single SFP transceiver on each switch because SFP and QSFP are interchangeable form factors
Show answer and explanation
Correct answer: A
Explanation
This scenario tests practical understanding of transceiver form factors and uplink planning. SFP is commonly associated with 1 Gbps interfaces, while SFP+ is commonly used for 10 Gbps, and QSFP+ is commonly used for 40 Gbps. In a data center uplink scenario where the goal is a single 40 Gbps connection with minimal cabling, a QSFP+ uplink is the appropriate choice when both ends support it. Network+ candidates should recognize that form factor compatibility depends on the switch hardware and the transceiver standard; inserting a different media type module does not increase port speed beyond the hardware design. Vendor hardware guides and transceiver compatibility matrices typically document supported SFP, SFP+, QSFP, and QSFP+ modules, along with whether breakout cables or link aggregation are supported.
- A. Correct.
Correct. QSFP+ is a quad small form-factor pluggable standard commonly used for 40 Gbps Ethernet. If both switches have compatible QSFP+ uplink ports, this provides a single high-speed uplink with fewer physical connections than aggregating multiple lower-speed links. This is the most direct way to meet the requirement.
- B. Incorrect.
Incorrect. Four SFP links can be combined with link aggregation in some environments, but that does not create a single native 40 Gbps interface. Standard SFP ports are typically 1 Gbps, and even SFP+ is 10 Gbps. Also, bundling multiple SFP links requires platform and protocol support and still uses multiple physical connections.
- C. Incorrect.
Incorrect. RJ45 copper transceivers do not convert a standard SFP uplink into a 40 Gbps connection. Copper module choice does not change the maximum speed of the switch port or make it equivalent to a QSFP+ interface.
- D. Incorrect.
Incorrect. SFP and QSFP are not interchangeable. They are different form factors and support different lane configurations and speeds depending on the specific standard. A switch port designed for SFP cannot simply accept a QSFP module, and vice versa, unless the hardware specifically supports breakout or compatibility modes.