LAN Switching Concepts! Trivia Quiz

1. Switch Internal Processing ------------------------------------

1 - Store and forward
2 - Fragment-free
3 - Cut-through
A - The switch fully receives all bits in the frame before forwarding the frame. This allows the switch to check the FCS before forwarding the frame.
B - The switch forwards the frame as soon as it can. This reduces latency but does not allow the switch to discard frames that fail the FCS check.
C - The switch forwards the frame after receiving the first 64 bytes of the frame, thereby avoiding forwarding frames that were errored due to a collision

1A 2B 3C

1A 2C 3B

1C 2B 3C

1B 2A 3C

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Explanation

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2. The IEEE defines 3 general categories of Ethernet MAC addresses 1 - Unicast 2 - Broadcast 3 - Multicast A) A frame sent with a destination address of the broadcast address (FFFF.FFFF.FFFF) implies that all devices on the LAN should receive and process the frame B) Allow a dynamic subnet of devices on a LAN to communicate C) MAC addresses that identify a single LAN interface card

1A 2B 3C

1C 2A 3B

1C 2AB 3B

1C 2B 3A

Unicast MAC addresses (1C) are used to identify a single LAN interface card. Broadcast MAC addresses (2A) are used to send a frame to all devices on the LAN. Multicast MAC addresses (3B) are used to allow a dynamic subnet of devices on a LAN to communicate. Therefore, the correct answer is 1C 2A 3B.

Explanation

Unicast MAC addresses (1C) are used to identify a single LAN interface card. Broadcast MAC addresses (2A) are used to send a frame to all devices on the LAN. Multicast MAC addresses (3B) are used to allow a dynamic subnet of devices on a LAN to communicate. Therefore, the correct answer is 1C 2A 3B.

3. Campus switches || 1 Access switches || || Distribution switches ||Core switches Connect Distribution switches to other building blocks and together Connect end devices Connect Access switches together

15 26 34

14 25 36

16 25 36

15 24 36

The given answer, 15 26 34, represents the connections between the different types of switches in a campus network. The first number, 15, indicates the connection between Access switches. The second number, 26, represents the connection between Distribution switches and other building blocks. Lastly, the third number, 34, signifies the connection between Core switches. This configuration allows for the Access switches to be connected together, the Distribution switches to connect to other building blocks, and the Core switches to be interconnected.

Explanation

The given answer, 15 26 34, represents the connections between the different types of switches in a campus network. The first number, 15, indicates the connection between Access switches. The second number, 26, represents the connection between Distribution switches and other building blocks. Lastly, the third number, 34, signifies the connection between Core switches. This configuration allows for the Access switches to be connected together, the Distribution switches to connect to other building blocks, and the Core switches to be interconnected.

4.

We call Fast Ethernet 1 is the interface the hub connected to the switch. Suppose the switch has no MAC addresses for any of the PCs shown in the picture. Suppose PC0 (connected to the hub) sends a frame to PC2 (also connected to the same hub). What will the switch do

The switch forwards the frame from PC0 to PC2

The hub forwards the frame from PC0 to PC2

The switch discards the frame

The switch forwards the frame to PC1, PC2, and PC3

The switch forwards the frame to PC2, and PC3

The switch forwards the frame to PC2, and PC3 because + it doesn't forward the frame back to where the frame comes from, which is PC1 + the switch doesn't have destination MAC addresses of any computer at all.

Explanation

The switch forwards the frame to PC2, and PC3 because + it doesn't forward the frame back to where the frame comes from, which is PC1 + the switch doesn't have destination MAC addresses of any computer at all.

5. Even though 10BASET is better than 10BASE5 and 10BASE2, it still has many problems such as

Broadcasts sent by 1 device is heard and process by only the intended devices on the network

Hub, used in 10BASET network allows all devices to send frame simultaneousnesly thus double the available bandwidth

Frame collision is inevitable in the network

UTP cable is unshielded and thus prone to more interference than co-ax cable in 10BASE5 and 10BASE2

Because hub is used in 10BASET network
- frame sent by 1 device is heard and processed by all devices. Only switch process frame, the hub doesn't.
- all devices share bandwidth so effective bandwidth is not double.
- the frame can only be sent 1 at a time

Explanation

Because hub is used in 10BASET network
- frame sent by 1 device is heard and processed by all devices. Only switch process frame, the hub doesn't.
- all devices share bandwidth so effective bandwidth is not double.
- the frame can only be sent 1 at a time

6. The difference between a hub and a bridge is that

Bridge creates more collision domain

Bridge creates only 1 collision domain

Hub creates more collision domain

Hub creates only 1 collision domain

Hub doubles the available bandwidth of the network

Bridge doubles the available bandwidth of the network

A hub creates more collision domains because it broadcasts all incoming signals to all connected devices, causing collisions when two or more devices try to transmit at the same time. On the other hand, a bridge creates only 1 collision domain by filtering and forwarding network traffic based on MAC addresses, preventing collisions. Additionally, a bridge doubles the available bandwidth of the network by creating a separate collision domain for each connected device, while a hub does not have this capability.

Explanation

A hub creates more collision domains because it broadcasts all incoming signals to all connected devices, causing collisions when two or more devices try to transmit at the same time. On the other hand, a bridge creates only 1 collision domain by filtering and forwarding network traffic based on MAC addresses, preventing collisions. Additionally, a bridge doubles the available bandwidth of the network by creating a separate collision domain for each connected device, while a hub does not have this capability.

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7.

(Ignore the color of the connected cables) Suppose none of the switches has any MAC addresses of any PCs in the picture. PC0 is turned off. It cannot receive or send any thing. When PC1 sends a frame to PC0. What will happen?

Switch 4 floods the frame to all connected interfaces

Switch 0 floods the frame to all connected interfaces

Switch 3 floods the frame to all connected interfaces

Switch 0 forwards the frame to PC0 and records the MAC of PC0 and the its connected interface

The frame will be flooded indefinitely. Because PC0 is turned off, it cannot reply to any switches. And since the switches do not know the MAC and interface of PC0, they will continually flood the frame throughout the network.

Explanation

The frame will be flooded indefinitely. Because PC0 is turned off, it cannot reply to any switches. And since the switches do not know the MAC and interface of PC0, they will continually flood the frame throughout the network.

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8. 10BASE2, 10BASE5, 10BASET.

10BASE2 and 10BASE5 uses a single cable to share network resources.

10BASET uses a shared hub to share network resources

10BASET uses co-ax cabling

10BASE2 and 10BASE5 uses UTP

In a 10BASE2 and 10BASE5, a problem happens on any single cable will affect the entire network

10BASET uses UTP
10BASE2 and 10BASE5 uses co-ax cabling

Explanation

10BASET uses UTP
10BASE2 and 10BASE5 uses co-ax cabling

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9. The switch learns MAC addresses and interfaces by

Examining the interface of the SOURCE MAC

Examining the DESTINATION MAC address in the frame

Examining the SOURCE MAC address in the frame

Examining the interface of the DESTINATION MAC

The switch learns MAC addresses and interfaces by examining the interface of the SOURCE MAC and examining the SOURCE MAC address in the frame. This means that the switch looks at the interface from which the frame is received and the MAC address of the device that sent the frame. By doing so, the switch can build a table that associates MAC addresses with the corresponding interfaces, allowing it to efficiently forward frames to the correct destination.

Explanation

The switch learns MAC addresses and interfaces by examining the interface of the SOURCE MAC and examining the SOURCE MAC address in the frame. This means that the switch looks at the interface from which the frame is received and the MAC address of the device that sent the frame. By doing so, the switch can build a table that associates MAC addresses with the corresponding interfaces, allowing it to efficiently forward frames to the correct destination.

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10. (3) Primary functions of a switch are

Routes the packet to appropriate device

Learns MAC addresses based on SOURCE address

Makes forwarding decision based on DESTINATION IP address

Makes forwarding decision based on DESTINATION MAC address

Uses STP (Spanning Tree Protocol) to prevents looping in a Layer 2 network environment

Creates collision domains and doubles available bandwidth

Creates collision domains and doubles available bandwidth are benefits of using a switch, not a switch's functions.
Routes the packet to appropriate device - switch routes frames, not packets. Router routes packets. The switch operates at layer 2 (frame). The router operates at layer 3 (packet)
Makes forwarding decision based on DESTINATION IP address - Layer 2 deals with MAC only. Layer 3 deals with IP.

Explanation

Creates collision domains and doubles available bandwidth are benefits of using a switch, not a switch's functions.
Routes the packet to appropriate device - switch routes frames, not packets. Router routes packets. The switch operates at layer 2 (frame). The router operates at layer 3 (packet)
Makes forwarding decision based on DESTINATION IP address - Layer 2 deals with MAC only. Layer 3 deals with IP.

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11.

We call Fast Ethernet 1 is the interface the hub connected to the switch. The switch in the picture has MAC addresses of all PC0, 1, 2, and 3 and all the interfaces that these PCs connected to. Suppose PC0 (connected to the hub) sends a frame to PC1 (also connected to the same hub). What will the switch do

The switch forwards the frame from PC0 to PC1.

The hub forwards the frame from PC0 to PC1.

The switch discards the frame

The hub simply regenerates the signal and forwards the frame to all connected interface, in this case it's PC1

The switch discards the frame because the frame comes from the same interface that it is sending out, interface 1. The switch simply does not forward the frame to the same interface the frame comes in.

Explanation

The switch discards the frame because the frame comes from the same interface that it is sending out, interface 1. The switch simply does not forward the frame to the same interface the frame comes in.

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12. Benefits of using a switch are (Pick 5)

Frame forwarding and filtering

More collision domains

Dedicated bandwidth to devices on each port

Uses store-and-forward, cut-through, and fragment-free internal processing methods to process frames

Multiple conversations between devices on different ports

Rate adaptation meaning devices using different speed can work with each other on the same network

Switch prevents loop in a switching network by using Spanning Tree Protocol

Double the available bandwidth of devices connected to it

Frame forwarding and filtering and Switch prevents loop in a switching network by using Spanning Tree Protocol - this is how switch deals with frames
Uses store-and-forward, cut-through, and fragment-free internal processing methods to process frames - this is how switch deals with frame internally

Explanation

Frame forwarding and filtering and Switch prevents loop in a switching network by using Spanning Tree Protocol - this is how switch deals with frames
Uses store-and-forward, cut-through, and fragment-free internal processing methods to process frames - this is how switch deals with frame internally

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