Ace Your Interview: Ethernet Questions and Answers

Here’s a compilation of frequently asked questions and detailed answers about Ethernet, designed to help you ace your job interview or prepare for engineering vivas.

Question 1: What is Ethernet?

Ethernet is a popular networking technology that defines the physical and data link layers within the OSI model. It enables communication between computers and devices within a Local Area Network (LAN) by transmitting data packets. This transmission occurs over a shared or dedicated medium, typically twisted-pair copper cables or fiber-optic cables.

Question 2: What are the different types of Ethernet cables?

Here are some common Ethernet cable types:

• Category 5e (Cat5e): Supports data rates up to 1 Gbps. It’s commonly found in homes and small businesses for Ethernet networking.
• Category 6 (Cat6): Supports data rates up to 10 Gbps, offering enhanced performance and greater bandwidth compared to Cat5e.
• Category 6a (Cat6a): Supports data rates up to 10 Gbps over longer distances, with improved noise resistance and crosstalk performance.
• Category 7 (Cat7): Supports data rates up to 10 Gbps and includes additional shielding for reduced interference, resulting in better performance in noisy environments.

Question 3: What is the difference between half-duplex and full-duplex Ethernet communication?

In half-duplex Ethernet communication, devices can either transmit or receive data, but not at the same time . This mode is commonly used in shared media environments where collisions are possible.

In full-duplex Ethernet communication, devices can transmit and receive data simultaneously . This allows for higher throughput and reduced latency.

Question 4: What is an Ethernet switch, and how does it differ from an Ethernet hub?

An Ethernet switch is a networking device that connects multiple devices within a LAN. It intelligently forwards data packets to their intended destinations based on their MAC addresses.

Unlike an Ethernet hub, which broadcasts data to all connected devices, a switch directs traffic only to the devices that need to receive it. This targeted approach leads to improved performance and reduced network congestion.

Question 5: What is Power over Ethernet (PoE), and what are its benefits?

Power over Ethernet (PoE) is a technology that allows Ethernet cables to carry electrical power alongside data. This enables devices like IP cameras, VoIP phones, and wireless access points to be powered through the same Ethernet cable.

Benefits of PoE include:

• Simplified installation
• Reduced cost and complexity of cabling infrastructure
• Increased flexibility in device placement

Question 6: What is an Ethernet frame, and what are its components?

An Ethernet frame is a data packet format used to transmit data over Ethernet networks. Its components include:

• Preamble: A sequence of alternating ones and zeros used for synchronization and timing recovery.
• Start Frame Delimiter (SFD): Marks the beginning of the Ethernet frame.
• Destination MAC Address: Identifies the intended recipient of the frame.
• Source MAC Address: Identifies the sender of the frame.
• EtherType or Length Field: Specifies the type of payload or the length of the frame.
• Payload: Contains the actual data being transmitted.
• Frame Check Sequence (FCS): A checksum value used for error detection.

Question 7: What is an Ethernet collision, and how is it handled in Ethernet networks?

An Ethernet collision occurs when two or more devices attempt to transmit data simultaneously on a shared Ethernet segment, leading to data corruption and loss.

Ethernet networks use the Carrier Sense Multiple Access with Collision Detection (CSMA/CD) protocol to detect and resolve collisions. When a collision is detected, devices involved wait a random amount of time before attempting to retransmit the data.

Question 8: What is an Ethernet MAC address, and how is it used in Ethernet networks?

An Ethernet MAC (Media Access Control) address is a unique identifier assigned to each Network Interface Controller (NIC) in a device. It’s used to identify devices on an Ethernet network and facilitate the delivery of data packets to their intended recipients. MAC addresses are typically 48 bits in length and are represented as hexadecimal numbers.

Question 9: What is Ethernet autonegotiation, and why is it important?

Ethernet autonegotiation is a feature that enables Ethernet devices to automatically negotiate and select the optimal network settings (speed, duplex mode, flow control) during the initial link establishment.

Autonegotiation helps ensure compatibility and optimal performance between devices with different capabilities, reducing the need for manual configuration and troubleshooting.

Question 10: How does Ethernet handle network congestion, and what are some methods for managing congestion?

Ethernet networks handle network congestion through techniques like flow control, congestion avoidance, and Quality of Service (QoS) mechanisms.

• Flow control mechanisms (e.g., Ethernet Pause Frames) allow devices to temporarily halt data transmission to prevent congestion.
• Congestion avoidance techniques (e.g., Random Early Detection (RED) and Explicit Congestion Notification (ECN)) help regulate traffic and prevent packet loss.
• Quality of Service (QoS) mechanisms prioritize certain types of traffic (e.g., voice or video) over others to ensure optimal performance for critical applications.