220-1101 Networking Practice Question
A technician is setting up a small office network. The ISP provides a cable modem with a single Ethernet port. The office has 15 computers that all need internet access. The technician has a router with four LAN ports and a 24-port unmanaged switch. Which of the following is the correct way to connect the devices to provide internet access to all computers?
⚠ Common exam trap
Candidates often think any Ethernet port on a router can accept the modem connection, not realizing the WAN port is specifically configured for external network access and that using a LAN port would break routing and NAT functionality.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Connect the modem to the router's WAN port, then connect the switch to one of the router's LAN ports, and connect all computers to the switch.
The router's WAN port is designed to connect to the ISP modem for public IP assignment via DHCP, while the LAN ports provide private IP addresses to internal devices. The switch connects to a LAN port to expand the number of available ports, allowing all 15 computers to access the internet through the router's NAT and routing functions.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Connect the modem to one of the router's LAN ports, then connect the switch to another LAN port, and connect all computers to the switch.
Why it's wrong here
If the modem is connected to a LAN port, the router treats it as a client device, not as an internet source, so it will not route traffic to the WAN or perform NAT for the network.
When this WOULD be correct
If the ISP provided a modem/router combo that already performs NAT and routing, and the technician only needs to extend the network, connecting the combo's LAN port to a router's LAN port (with DHCP disabled on the router) would work as a switch/access point.
- ✓
Connect the modem to the router's WAN port, then connect the switch to one of the router's LAN ports, and connect all computers to the switch.
Why this is correct
This is the standard and only correct cabling order for a typical cable ISP connection. The modem bridges the coaxial cable to an Ethernet WAN link, handing the router's WAN port a single public IP address. The router then uses NAT (Network Address Translation) to multiplex all internal devices onto that one public IP and acts as a DHCP server, while the switch—connected to a LAN port—simply expands the routed broadcast domain so every computer can reach the internet through the router.
- ✗
Connect the modem directly to the switch, then connect the router to the switch, and connect all computers to the router's LAN ports.
Why it's wrong here
Connecting the modem directly to the switch exposes the modem's single public IP to the network, but the switch cannot perform NAT; the router would also be connected incorrectly, likely not getting a public IP.
When this WOULD be correct
If the ISP provided a modem/router combo that already performs NAT and routing, and the additional router is to be used as a switch or access point, then connecting the modem to the switch and the router to the switch could be correct, with the router's WAN port disabled and LAN ports used for clients.
- ✗
Connect the modem to one of the switch's ports, then connect the router to another switch port, and connect all computers to the router.
Why it's wrong here
Similar to option C, this configuration fails to properly separate the WAN and LAN. The router may get a public IP but network traffic flow would be incorrect, and the router's LAN ports are limited to four.
When this WOULD be correct
This option would be correct if the question specified that the router is used only as a switch (with routing disabled) and the modem has a built-in router/firewall. In that case, the modem handles routing, and the router acts as an additional switch to expand ports.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The 220-1101 exam frequently reuses these exact scenarios with slightly different constraints.
✓Connect the modem to the router's WAN port, then connect the switch to one of the router's LAN ports, and connect all computers to the switch.Correct answer▾
Why this is correct
This is the standard and only correct cabling order for a typical cable ISP connection. The modem bridges the coaxial cable to an Ethernet WAN link, handing the router's WAN port a single public IP address. The router then uses NAT (Network Address Translation) to multiplex all internal devices onto that one public IP and acts as a DHCP server, while the switch—connected to a LAN port—simply expands the routed broadcast domain so every computer can reach the internet through the router.
✗Connect the modem to one of the router's LAN ports, then connect the switch to another LAN port, and connect all computers to the switch.Wrong answer — click to see why▾
Why this is wrong here
Connecting the modem to a router's LAN port bypasses NAT and routing, so the router cannot assign public IPs or provide internet access to multiple devices; only one computer would get a public IP.
★ When this WOULD be the correct answer
If the ISP provided a modem/router combo that already performs NAT and routing, and the technician only needs to extend the network, connecting the combo's LAN port to a router's LAN port (with DHCP disabled on the router) would work as a switch/access point.
Why candidates choose this
Candidates may think all ports on a router are equivalent or that the router's LAN ports can accept a modem connection, misunderstanding the distinct roles of WAN vs LAN ports.
✗Connect the modem directly to the switch, then connect the router to the switch, and connect all computers to the router's LAN ports.Wrong answer — click to see why▾
Why this is wrong here
Connecting the modem directly to the switch would assign public IP addresses to all devices, which is not feasible for a small office with 15 computers. The router must be between the modem and the switch to perform NAT and routing.
★ When this WOULD be the correct answer
If the ISP provided a modem/router combo that already performs NAT and routing, and the additional router is to be used as a switch or access point, then connecting the modem to the switch and the router to the switch could be correct, with the router's WAN port disabled and LAN ports used for clients.
Why candidates choose this
Candidates may think that the switch can distribute the internet connection directly, misunderstanding the need for a router to handle network address translation and routing between the public and private networks.
✗Connect the modem to one of the switch's ports, then connect the router to another switch port, and connect all computers to the router.Wrong answer — click to see why▾
Why this is wrong here
Connecting the modem to the switch and then the router to the switch would place the router's WAN port on the same broadcast domain as the modem, preventing proper NAT and routing. The router must be directly connected to the modem via its WAN port to obtain a public IP and provide internet access to the LAN.
★ When this WOULD be the correct answer
This option would be correct if the question specified that the router is used only as a switch (with routing disabled) and the modem has a built-in router/firewall. In that case, the modem handles routing, and the router acts as an additional switch to expand ports.
Why candidates choose this
Candidates may think that the switch can connect to the modem first and then distribute the internet connection to the router, not realizing that the router needs to be the gateway between the modem and the internal network for proper network address translation.
Analysis generated from the official 220-1101blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 220-1101 practice question is part of Courseiva's free CompTIA certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 220-1101 exam.