Identifying Layer 1 Issues on the OC-12 Circuit
Question
A telecommunications provider has just deployed a new OC-12 circuit at a customer site.
While the circuit showed no errors from the provider end to the customer's demarcation point, a network administrator is trying to determine the cause of dropped packets and errors on the circuit.
Which of the following should the network administrator do to rule out any problems at Layer 1? (Choose two.)
A.
Use a loopback at the demark and router, and check for a link light B.
Use an OTDR to validate the cable integrity C.
Use a pinout tester to validate the cable integrity D.
Use a multimeter to validate the cable integrity E.
Check for any devices that may be causing EMI on the cable F.
Clean the cables to be sure they are free of dust and debris.
AB.
Explanations
A telecommunications provider has just deployed a new OC-12 circuit at a customer site.
While the circuit showed no errors from the provider end to the customer's demarcation point, a network administrator is trying to determine the cause of dropped packets and errors on the circuit.
Which of the following should the network administrator do to rule out any problems at Layer 1? (Choose two.)
A.
Use a loopback at the demark and router, and check for a link light
B.
Use an OTDR to validate the cable integrity
C.
Use a pinout tester to validate the cable integrity
D.
Use a multimeter to validate the cable integrity
E.
Check for any devices that may be causing EMI on the cable
F.
Clean the cables to be sure they are free of dust and debris.
AB.
To rule out any problems at Layer 1 (Physical layer) of the Open Systems Interconnection (OSI) model, the network administrator should perform the following two tasks:
A. Use a loopback at the demarc and router, and check for a link light: A loopback test is a diagnostic tool used to test the physical connectivity between two devices by transmitting data from one device and receiving it on the same device. By using a loopback at the demarc and router, the network administrator can ensure that the cable and network interface cards are functioning correctly. Checking for a link light confirms that the two devices are communicating, and there are no physical connectivity issues between them.
B. Use an OTDR to validate the cable integrity: An Optical Time Domain Reflectometer (OTDR) is a test instrument that uses light pulses to measure the distance to a fiber optic cable's end and locate any breaks or faults in the cable. By using an OTDR, the network administrator can determine if there are any issues with the cable itself, such as a break or a faulty connector.
The other options are not relevant to testing Layer 1 issues: C. A pinout tester is used to test cables for proper wiring configurations. D. A multimeter is used to test electrical circuits and cannot be used to test fiber optic cables. E. EMI (Electromagnetic Interference) can affect the transmission of data on a cable, but it is not a Layer 1 issue. F. Cleaning cables is important, but it will not help in troubleshooting Layer 1 issues.
