220-1101 Question 138
Single answerOptical network terminal (ONT)A technician is installing internet service for a small office that was recently upgraded to fiber. The provider's optical network terminal (ONT) is mounted on the wall and shows normal optical link status. The customer connects a laptop directly to the ONT's Ethernet port and confirms internet access works. However, when the technician connects the office wireless router's WAN/Internet port to the ONT, none of the office devices can reach the internet. The router powers on and the local Wi-Fi network works normally. Which of the following is the BEST next step to restore internet access through the router?
- A
Replace the ONT because it is failing to convert the optical signal to Ethernet for the router
- B
Power cycle the ONT and then reconnect the router so the service can register the router's WAN interface
- C
Move the router cable from the WAN/Internet port to one of the router's LAN ports
- D
Change the router's Wi-Fi channel to reduce interference with the fiber signal
Show answer and explanation
Correct answer: B
Explanation
An ONT converts the ISP's fiber-optic connection into customer-usable services such as Ethernet for internet access. In this scenario, the ONT and fiber circuit are functioning because a directly connected laptop can browse successfully. The failure occurs only when swapping from the laptop to the router, which points to a device-registration or DHCP lease issue on the Ethernet handoff rather than a failed ONT. A common best practice is to connect the router's WAN/Internet port to the ONT, then power cycle the ONT so it can establish service with the router's WAN MAC address. This aligns with typical ISP installation and support procedures for residential and small-office fiber handoffs. If the issue remains after rebooting the ONT and router, the next steps would include verifying the router's WAN settings and confirming with the ISP whether PPPoE, VLAN tagging, or MAC registration is required.
- A. Incorrect.
This is incorrect. The ONT is already proving it can convert the provider's fiber signal to Ethernet because a laptop connected directly to the ONT has internet access. That indicates the fiber link and ONT function are working. Replacing the ONT would not be the best first troubleshooting step.
- B. Correct.
This is correct. In many fiber deployments, the ONT hands off service over Ethernet and the ISP may associate service with the connected device's MAC address until the session is cleared or the ONT is rebooted. If a laptop was connected first, the router may not obtain connectivity until the ONT is power cycled and allowed to establish a new Ethernet handoff to the router's WAN interface. This is a practical first step before escalating to the ISP.
- C. Incorrect.
This is incorrect. The router should connect to the ONT using the router's WAN/Internet port, not a LAN port. Connecting the ONT to a LAN port can bypass routing functions, create addressing problems, or prevent proper internet sharing depending on the router design. This reflects a common misconception between WAN uplink and LAN switch ports.
- D. Incorrect.
This is incorrect. Wi-Fi channel settings affect local wireless performance between client devices and the router, not the Ethernet handoff between the ONT and the router's WAN port. Fiber service does not experience radio-frequency interference from the router's Wi-Fi channel in this way.