Customer Premises Equipment, Servicing and Fault Diagnosis
This section covers Customer Premises Equipment, Servicing and Fault Diagnosis. The exam tests installation of ONTs, routers, and phones, and a logical method for isolating faults at the customer end.
Core rules and concepts
- CPE includes telephone instruments, DSL modems, ONTs, Wi-Fi routers, IP phones, splitters, and set-top boxes. Check power, line/port, credentials, and Wi-Fi settings.
- FTTH ONT LEDs: power, PON (registration), LOS (loss of signal), LAN, Wi-Fi. Solid PON means the optical link is registered; red LOS means fiber break, dirty connector, or unplugged patch cord.
- DSL: check sync, SNR margin, attenuation, and CRC errors. Low SNR margin or high attenuation points to line problems, not the router.
- Fault diagnosis: gather symptoms, check layer by layer (power, physical, link, IP, application), substitute known-good parts, and confirm with ping/traceroute and speed tests.
- Customer handling: explain the fault, avoid unnecessary replacements, log the ticket, and escalate with evidence.
Worked example
A customer reports no internet. The ONT power LED is on, PON LED is off, LOS is red. Reasoning: the optical link is down, so router settings are irrelevant. Check the patch cord at ONT and splitter, clean connectors, and test with a power meter. If no light, escalate to the fiber team. If PON later goes solid but ping fails, check PPPoE credentials and WAN configuration.
Traps that cost marks
Replacing the router before checking LOS/PON; confusing PON and LOS; ignoring Wi-Fi interference when only wireless fails; resetting a device without recording settings; and closing a ticket without confirming service.