Interface & Hardware Issues

Question 1

Monitoring the Network Interface

Answer 1

Observing interface performance using tools such as Simple Network Management Protocol (SNMP), switch port counters, and system logs to detect drops, errors, or abnormal activity.

Question 2

Link Status

Answer 2

Shows whether a network interface is up or down; a down status usually indicates cabling problems, power issues, speed/duplex mismatches, or device failure.

Question 3

The Ethernet Frame Structure

Answer 3

7 bytes that synchronize communication.

Start Frame Delimiter (SFD): Marks the start of the frame.

Destination MAC: Address of the receiving device.

Source MAC: Address of the sending device.

Type: Identifies the upper-layer protocol like IPv4 or IPv6.

Payload: The actual data being carried.

Frame Check Sequence (FCS): A Cyclic Redundancy Check (CRC) used to detect errors.

Question 4

CRC

Answer 4

Cyclic Redundancy Check (CRC) → An error-detecting method inside the Frame Check Sequence that verifies data integrity and checks whether the Ethernet frame was altered or corrupted.

Question 5

Ethernet Frame Sizes

Answer 5

Runts: Less than 64 bytes

Standard: 64–1500 bytes

Giants: More than 1518 bytes

Jumbo Frames: 1500–9000 bytes, used for high-performance networks.

Question 6

Error Disabled

Answer 6

A switch port state where the port is automatically shut down due to problems such as port security violations, bad cables, or excessive errors.

Question 7

PoE

Answer 7

Power over Ethernet (PoE) → Technology that provides electrical power through Ethernet cabling. Endspans are switches with built-in PoE, while midspans are separate power injectors placed between devices.

Question 8

PoE, PoE+, PoE++

Answer 8

PoE provides 15.4 watts

PoE+ provides 25.5 watts

PoE++ provides 51 watts or 71.3 watts, depending on the version.

Question 9

PoE Switch

Answer 9

A network switch with built-in Power over Ethernet (PoE) capability that supplies power and data to devices like access points, cameras, and phones over the same cable.

Question 10

Single Mode vs Multimode Transceivers

Answer 10

Single-mode fiber typically uses 1310 nm or 1550 nm wavelengths for long-distance connections.

Multimode fiber commonly uses 850 nm or 1300 nm wavelengths for shorter distances.