220-1101 Question 136
Single answerCable modemA technician is troubleshooting a home internet outage. The customer has a separate cable modem and wireless router. The wireless router appears to be working normally, but all devices show "No Internet." On the cable modem, the Power light is solid, the Downstream light is blinking continuously, and the Online light is off. The coaxial cable was recently moved when the customer rearranged furniture. Which of the following is the BEST next step for the technician?
- A
Replace the wireless router because the modem is not assigning IP addresses
- B
Verify the coaxial connection from the wall outlet to the cable modem and check for a damaged or loose connector
- C
Log in to the router and change the SSID to restore the ISP connection
- D
Disable DHCP on the router so the cable modem can provide addresses directly
Show answer and explanation
Correct answer: B
Explanation
The modem LEDs provide the key troubleshooting clues. In a typical DOCSIS cable modem sequence, the modem powers on, acquires downstream and upstream channels, and then establishes online status with the ISP. A continuously blinking Downstream light and an unlit Online light indicate the modem has not completed synchronization with the provider. Because the customer recently moved the equipment, the most likely and most appropriate initial action is to inspect the physical coax connection for looseness or damage. This aligns with standard CompTIA A+ troubleshooting methodology: start with the most likely and simplest physical causes before replacing equipment or changing configurations. ISP and modem vendor documentation commonly describes blinking downstream indicators as a signal acquisition problem, often tied to coax connectivity, splitters, or line issues.
- A. Incorrect.
This is incorrect. The modem status lights indicate the issue is occurring before the router would receive internet service. A blinking Downstream light and no Online light typically suggest the modem is not establishing synchronization with the cable provider, often due to a coax signal problem rather than a router failure or DHCP issue.
- B. Correct.
This is correct. A cable modem must lock onto the provider's downstream signal over the coax connection before it can come online. Since the coax was recently moved and the modem shows a blinking Downstream light with no Online light, the most appropriate first step is to inspect and reseat the coax cable, check for bent center conductors, loose F-connectors, or damage at the wall jack and modem.
- C. Incorrect.
This is incorrect. Changing the SSID only affects the wireless network name and has no effect on the cable modem's ability to synchronize with the ISP. The router's wireless functionality can appear normal even when the internet uplink is down.
- D. Incorrect.
This is incorrect. In a typical home setup, the router provides DHCP addresses to local devices, while the cable modem bridges the ISP connection. Disabling DHCP on the router would not help the modem acquire a downstream signal or register online with the provider.