Which segment is tested after validating the loopback at the CSU/DSU?

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Multiple Choice

Which segment is tested after validating the loopback at the CSU/DSU?

When you’re troubleshooting a WAN link, you test the path in logical order from the customer premises outward. A loopback test on the CSU/DSU confirms that the device itself and the transmission line up to the customer boundary are functioning correctly. Once that check passes, the next segment to verify is the inside plant—the cable running from the Demarc point to the MDF. This inside wiring and connections can easily hide faults like loose connectors, damaged cables, or bad patches, and testing this segment isolates whether the problem is within the customer’s building rather than beyond the Demarc. The edge router is farther down the line, behind the MDF, so it isn’t the immediate next test after a successful CSU/DSU loopback. The Demarc point is simply the boundary between provider and customer responsibilities, not a specific test segment. The service provider’s POP is outside the customer facility and not the focus of testing the internal path after a CSU/DSU loopback.

When you’re troubleshooting a WAN link, you test the path in logical order from the customer premises outward. A loopback test on the CSU/DSU confirms that the device itself and the transmission line up to the customer boundary are functioning correctly. Once that check passes, the next segment to verify is the inside plant—the cable running from the Demarc point to the MDF. This inside wiring and connections can easily hide faults like loose connectors, damaged cables, or bad patches, and testing this segment isolates whether the problem is within the customer’s building rather than beyond the Demarc.

The edge router is farther down the line, behind the MDF, so it isn’t the immediate next test after a successful CSU/DSU loopback. The Demarc point is simply the boundary between provider and customer responsibilities, not a specific test segment. The service provider’s POP is outside the customer facility and not the focus of testing the internal path after a CSU/DSU loopback.

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