If the WAN circuit is down but the provider reports the circuit is good, which component is most likely at fault on the customer side?

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Multiple Choice

If the WAN circuit is down but the provider reports the circuit is good, which component is most likely at fault on the customer side?

When the service provider reports that the WAN circuit is good, the issue is most likely on the customer’s side, specifically the device that actually connects the network to that circuit. The demarcation point is where provider responsibility ends and customer responsibility begins. If the provider has verified the line up to that boundary is fine, problems caused by the internal wiring or provider equipment are unlikely. The MDF is an internal building wiring hub; while issues there can cause outages, they’re typically evident to anyone troubleshooting inside the customer space and aren’t the first suspicion when the provider confirms the circuit itself is healthy. The service provider is not the culprit in this scenario because they’ve already indicated the circuit is good. The most plausible culprit on the customer side is the Customer Edge Router—the device that interfaces the WAN link to the customer network. If the line is up but traffic isn’t flowing correctly, the CE router (misconfiguration, faulty hardware, or a bad connection) is the likely fault, since it is the critical point where the provider’s service meets the customer’s network.

When the service provider reports that the WAN circuit is good, the issue is most likely on the customer’s side, specifically the device that actually connects the network to that circuit. The demarcation point is where provider responsibility ends and customer responsibility begins. If the provider has verified the line up to that boundary is fine, problems caused by the internal wiring or provider equipment are unlikely. The MDF is an internal building wiring hub; while issues there can cause outages, they’re typically evident to anyone troubleshooting inside the customer space and aren’t the first suspicion when the provider confirms the circuit itself is healthy. The service provider is not the culprit in this scenario because they’ve already indicated the circuit is good.

The most plausible culprit on the customer side is the Customer Edge Router—the device that interfaces the WAN link to the customer network. If the line is up but traffic isn’t flowing correctly, the CE router (misconfiguration, faulty hardware, or a bad connection) is the likely fault, since it is the critical point where the provider’s service meets the customer’s network.

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