Quick Answer
The answer is Ethernet (RJ45). This is the correct interface because a fiber optic router connection type relies on the Optical Network Terminal (ONT) to convert the incoming optical light signals into standard electrical signals, which the router then receives through a standard Ethernet port. On the CompTIA A+ Core 1 220-1201 exam, this question tests your understanding of how different WAN technologies physically connect to customer premises equipment; a common trap is confusing the fiber patch cable that links the ONT to the wall with the router’s connection, or mistakenly choosing coaxial (cable internet) or RJ11 (DSL). Remember that the ONT acts as a media converter, so the router always connects to it via a twisted-pair Ethernet cable. A simple memory tip: think “ONT to Router = RJ45,” because the fiber stops at the ONT, and copper Ethernet takes over from there.
This 220-1201 practice question tests your understanding of internet connection types. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A technician is configuring a new router for a client who has a fiber-optic internet connection. Which type of interface is most likely used to connect the router to the ISP's ONT (Optical Network Terminal)?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Coaxial (F-type)
Why wrong: Coaxial is used for cable internet, not fiber.
RJ11 (phone jack)
Why wrong: RJ11 is used for DSL connections, not fiber.
Ethernet (RJ45)
The ONT outputs Ethernet to connect to a router for fiber internet.
Fiber patch cable (LC connector)
Why wrong: Fiber patch cables connect the ONT to the wall, not typically directly to a router.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Ethernet (RJ45)
Fiber-optic connections typically use an ONT that converts optical signals to electrical, and the router connects via Ethernet (RJ45). Coaxial is for cable, RJ11 for DSL, and fiber patch cables connect the ONT to the wall, not the router. Ethernet is the standard interface for modern fiber installations.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
Coaxial (F-type)
Why it's wrong here
Coaxial is used for cable internet, not fiber.
RJ11 (phone jack)
Why it's wrong here
RJ11 is used for DSL connections, not fiber.
Ethernet (RJ45)
Why this is correct
The ONT outputs Ethernet to connect to a router for fiber internet.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Static NAT maps one inside address to one outside address.
Fiber patch cable (LC connector)
Why it's wrong here
Fiber patch cables connect the ONT to the wall, not typically directly to a router.
Common exam traps
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Detailed technical explanation
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Real-world example
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
What to study next
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related 220-1201 NAT questions on configuration and troubleshooting.
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FAQ
Internet Connection Types — This question tests Internet Connection Types — Static NAT maps one inside address to one outside address..
The correct answer is: Ethernet (RJ45) — Fiber-optic connections typically use an ONT that converts optical signals to electrical, and the router connects via Ethernet (RJ45). Coaxial is for cable, RJ11 for DSL, and fiber patch cables connect the ONT to the wall, not the router. Ethernet is the standard interface for modern fiber installations.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related 220-1201 NAT questions on configuration and troubleshooting.
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Static NAT maps one inside address to one outside address.
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Last reviewed: Jun 18, 2026
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