Ethernet Switching

Question 1

At which OSI layer does Ethernet switching operate?

Answer 1

Layer 2 – the Data Link Layer.

Question 2

What are the primary functions of Ethernet switching?

Answer 2

• LAN data transmission
• Managing broadcast and collision domains
• Supporting switching/security technologies

Question 3

What is CSMA/CD?

Answer 3

Carrier Sense Multiple Access with Collision Detection – devices listen before sending and retransmit if a collision occurs.

Question 4

How do hubs and switches differ in collision domains?

Answer 4

Hubs share one collision domain; switches provide one per port.

Question 5

What is the difference in duplex mode between hubs and switches?

Answer 5

Hubs operate in half duplex; switches use full duplex (simultaneous send/receive).

Question 6

What protocol replaced older Layer 2 technologies like Token Ring?

Answer 6

Ethernet.

Question 7

What is the function of a hub?

Answer 7

Operates at Layer 1, broadcasting to all ports with no filtering.

Question 8

What does a bridge do?

Answer 8

Layer 2 device that forwards frames based on MAC addresses and splits collision domains.

Question 9

How is a switch different from a bridge?

Answer 9

A switch is a multi-port bridge, creating a separate collision domain per port.

Question 10

What is the purpose of a router?

Answer 10

Operates at Layer 3 to route packets and break up broadcast domains.

Question 11

What is a Layer 3 switch?

Answer 11

A switch with routing capabilities, ideal for SOHO and VLAN routing.

Question 12

What does a media converter do?

Answer 12

Converts between different media types (fiber, coaxial, copper).

Question 13

What is a VLAN?

Answer 13

A logical network segment at Layer 2 that separates broadcast domains.

Question 14

What are four benefits of VLANs?

Answer 14

• Improved security
• Better performance
• Easier management
• Cost efficiency

Question 15

What is 802.1Q tagging?

Answer 15

Adds VLAN IDs to Ethernet frames for trunking.

Question 16

What is the Native VLAN?

Answer 16

The VLAN used for untagged traffic on trunk ports (default: VLAN 1).

Question 17

What is a Voice VLAN?

Answer 17

A VLAN that prioritizes VoIP traffic using Quality of Service (QoS).

Question 18

What is an SVI?

Answer 18

Switch Virtual Interface – enables Layer 3 routing between VLANs.

Question 19

What is a trunk port?

Answer 19

Carries traffic for multiple VLANs using 802.1Q tags.

Question 20

What is an access port?

Answer 20

Assigned to a single VLAN only.

Question 21

What are some VLAN configuration best practices?

Answer 21

• Change the default Native VLAN
• Block unused VLANs
• Enable QoS for voice

Question 22

What is link aggregation?

Answer 22

Combining multiple switch ports into one logical connection for increased bandwidth and redundancy.

Question 23

What is the preferred setting for speed and duplex?

Answer 23

Auto-negotiation is preferred, but manual settings can be used for legacy devices or troubleshooting.

Question 24

What is the purpose of STP?

Answer 24

To prevent switching loops and broadcast storms in redundant networks.

Question 25

What are the variants of STP?

Answer 25

* STP (802.1D): ~50s convergence * RSTP (802.1w): <10s convergence * MSTP (802.1s): Multiple VLANs in one instance * PVST+ (Cisco): One STP per VLAN

Question 26

What is the Root Bridge in STP?

Answer 26

The central switch with the lowest Bridge ID.

Question 27

What are the three main STP port roles?

Answer 27

* Root Port (best path to root) * Designated Port (forwarding) * Non-Designated Port (blocking)

Question 28

What are the four STP port states?

Answer 28

* Blocking * Listening * Learning * Forwarding

Question 29

What does NAC do?

Answer 29

Ensures only authorized and compliant devices can connect to the network.

Question 30

What is port security?

Answer 30

Restricts the number of MAC addresses per switch port.

Question 31

What does MAC filtering do?

Answer 31

Allows or blocks specific MAC addresses.

Question 32

What is 802.1X used for?

Answer 32

Network access control using RADIUS authentication.

Question 33

What are persistent and non-persistent agents in NAC?

Answer 33

* Persistent: Installed on corporate devices * Non-persistent: Temporary, often used in BYOD scenarios

Question 34

What other types of NAC controls exist?

Answer 34

* Time-based * Location-based * Role-based (RBAC) * Rule-based policies

Question 35

What is the MTU?

Answer 35

The maximum frame size (in bytes) that can be transmitted on a network.

Question 36

What are standard MTU sizes?

Answer 36

* Ethernet: 1500 bytes * Wireless: 1400–1420 bytes * VPN/PPPoE: 1400–1450 bytes * Jumbo Frames: 9000 bytes

Question 37

What is fragmentation and why is it a concern?

Answer 37

Occurs when frames exceed MTU, causing extra overhead and performance issues.

Question 38

How can you test MTU size on a network?

Answer 38

Use the ping command with -f (do not fragment) and -l (packet size) flags.

Question 39

What is a switch?

Answer 39

A Layer 2 device that forwards traffic based on MAC addresses.

Question 40

What is a trunk port?

Answer 40

A port that carries traffic from multiple VLANs using 802.1Q tags.

Question 41

What is STP?

Answer 41

A protocol that prevents Layer 2 loops using port roles and states.

Question 42

What is NAC?

Answer 42

Network Access Control – controls access through device and user validation.

Question 43

What is SVI?

Answer 43

Switch Virtual Interface – a virtual interface for VLAN communication on switches.

Question 44

What is the purpose of VLANs?

Answer 44

To segment networks logically at Layer 2 for performance and security.

Question 45

What does MTU impact in networking?

Answer 45

It affects fragmentation, which can influence network performance.

Question 46

What layer do VLANs operate on?

Answer 46

Layer 2.

Question 47

What layer do routers operate on?

Answer 47

Layer 3.

Question 48

What criteria does STP use to elect the root bridge?

Answer 48

The lowest Bridge ID.

Question 49

What are common NAC methods?

Answer 49

* 802.1X * MAC filtering * Port security

Question 50

Why use link aggregation?

Answer 50

For increased bandwidth and redundancy.

Question 51

Which STP variants are recommended for modern networks?

Answer 51

RSTP or PVST+.