Detect Link

Context

Virtual cable test (VCT) technology uses time domain reflectometry (TDR) to detect the cable status. When a pulse is transmitted to the end of a cable or a failure point in the cable, some pulse energies are reflected to the transmitting end. The VCT algorithm measures the time spent on transmitting pulses over a cable, reaching a failure point, and returning the pulses. The measured time is converted to the distance.

VCT can detect the fault type of a network cable and identify failure points to help locate network cable faults.

The VCT test result is only for reference and may be inaccurate for cables of some vendors.

VCT takes effect only on optical interfaces that have GE copper modules installed or GE electrical interfaces on the device.

Procedure

Click Configuration in the function area and choose Interface Setting > Detect Link from the navigation tree in the left. The Detect Link is displayed.
Select the interface that you want to configure. Perform either of the following operations as required.
- Click an interface icon to select an interface.
- Drag the mouse to select multiple consecutive interfaces in a batch.
- Select an interface card name to select all the interfaces on the interface card.
Click Start Detection to complete the configuration.

You can view check results on the Configure interface.

Table 1 describes the parameters on the Configure interface.

**Table 1** Parameters on the **Configure interface**
Item	Description
Interface	Type and number of the interface on which link detection is performed.
Management status	Management status of the interface. down: The interface is disabled. up: The interface is enabled. administratively down: indicates that the administrator has run the shutdown command on the interface.
Detection result	Detection result. Possible results are as follows: The network cable is faulty. You can click Details to view the detailed detection result. The Details contains the following fields: Pair A/B/C/D: Four pairs of circuits in a network cable. Pair A length: Length of a network cable. The length is the distance between the interface and the fault point if a fault occurs. The length is the actual length of the cable when the cable works properly. The default length is 0 m if the interface is not connected to any network cable. Pair A state: Network cable status. Ok: The circuit pair is terminated properly. Open: The circuit pair is not terminated. Short: The circuit pair is short-circuited. Crosstalk: The cable sequence is incorrect. Unknown: An unknown fault occurs on the circuit pair. The network cable work normally.