Network Infrastructure: Layer 2 Ethernet Switches

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Questions and Answers

What is the primary function of a layer 2 Ethernet switch?

  • To route data between subnets
  • To provide network access to wireless devices
  • To forward data based on MAC addresses (correct)
  • To translate IP addresses to DNS names

What is the length of a MAC address in bits?

  • 32 bits
  • 24 bits
  • 64 bits
  • 48 bits (correct)

What command can be used to display the physical address of a network interface card on a Windows device?

  • ping -l
  • ipconfig /all (correct)
  • ipconfig /dns
  • tracert -d

What is the purpose of an access point in a network?

<p>To provide network access to wireless devices (A)</p> Signup and view all the answers

What is the representation of a MAC address?

<p>12 hexadecimal characters (B)</p> Signup and view all the answers

What is the layer 2 address also known as?

<p>Physical address (B), MAC address (C)</p> Signup and view all the answers

What is the primary difference between a layer 2 switch and a router?

<p>A layer 2 switch forwards data based on MAC addresses, while a router forwards data based on IP addresses (C)</p> Signup and view all the answers

What is the function of Switch 1 and Switch 2 in the network topology?

<p>To forward data based on MAC addresses (D)</p> Signup and view all the answers

What is the primary function of a layer 2 switch in a network?

<p>To connect multiple devices together and allow them to communicate (A)</p> Signup and view all the answers

What is the benefit of having separate collision domains in a network?

<p>Improved network performance (C)</p> Signup and view all the answers

What is the purpose of ARP in a network?

<p>To resolve IP addresses to layer 2 addresses (C)</p> Signup and view all the answers

What is the advantage of full duplex communication in a network?

<p>Improved network performance (A)</p> Signup and view all the answers

What is the default behavior of a layer 2 switch in terms of broadcast domains?

<p>One broadcast domain for the entire switch (A)</p> Signup and view all the answers

What is the purpose of a broadcast in a network?

<p>To send data to all devices on the network (A)</p> Signup and view all the answers

What is the function of the backplane in a switch?

<p>To buffer data during congestion (D)</p> Signup and view all the answers

What is the benefit of using a layer 2 switch over a hub in a network?

<p>Improved network performance (B)</p> Signup and view all the answers

What is the primary purpose of a layer 2 switch in a network topology?

<p>To forward frames of data based on layer 2 addresses (C)</p> Signup and view all the answers

What is the purpose of VLANs in a network?

<p>To divide a switch into multiple broadcast domains (C)</p> Signup and view all the answers

What is the term for the address assigned by the manufacturer of a network interface card?

<p>Burned-in address (BIA) (A)</p> Signup and view all the answers

What information does a layer 2 switch use to make forwarding decisions?

<p>Destination MAC address (A)</p> Signup and view all the answers

What is the advantage of using unshielded twisted pair (UTP) cables in a network?

<p>Full duplex communication (D)</p> Signup and view all the answers

What is the purpose of a switch building a table of layer 2 addresses and corresponding ports?

<p>To enable efficient forwarding of frames of data (B)</p> Signup and view all the answers

What is the term for the address that identifies a network interface card at layer 2?

<p>MAC address (B)</p> Signup and view all the answers

What is the benefit of using a layer 2 switch instead of a hub?

<p>Improved network efficiency through targeted forwarding (B)</p> Signup and view all the answers

What is the term for the process of a device sending a frame of data into the network, including the source and destination layer 2 addresses?

<p>Frame transmission (A)</p> Signup and view all the answers

What is the purpose of a PC performing an ARP request?

<p>To obtain the MAC address of the default gateway (A)</p> Signup and view all the answers

What is the role of the switch in forwarding a frame of data from a PC to the default gateway?

<p>To forward the frame to the correct port based on the destination MAC address (D)</p> Signup and view all the answers

What is the term for the address that a network interface card uses to identify itself at layer 2?

<p>MAC address (B)</p> Signup and view all the answers

What is a characteristic of a switch that makes it better than a hub?

<p>It has full duplex capabilities (A)</p> Signup and view all the answers

What is the number of collision domains on a 48-port switch?

<p>48 (C)</p> Signup and view all the answers

What is the number of broadcast domains on a 48-port switch by default?

<p>1 (A)</p> Signup and view all the answers

What is the purpose of a switch learning layer 2 addresses?

<p>To make forwarding decisions based on layer 2 addresses (B)</p> Signup and view all the answers

What command can be used to show the layer 2 addresses learned by a switch?

<p>show mac address-table (B)</p> Signup and view all the answers

What is the significance of a switch having full duplex capabilities?

<p>It can send and receive data simultaneously (B)</p> Signup and view all the answers

What is the purpose of a switch storing layer 2 addresses in a table?

<p>To make forwarding decisions based on layer 2 addresses (C)</p> Signup and view all the answers

What happens when a device sends a broadcast on a layer 2 switch?

<p>The switch forwards the broadcast to all devices (B)</p> Signup and view all the answers

What is the significance of a switch having 48 ports?

<p>It can forward data to 48 devices (A)</p> Signup and view all the answers

What is the purpose of a switch dynamically learning layer 2 addresses?

<p>To make forwarding decisions based on layer 2 addresses (A)</p> Signup and view all the answers

What is the reason why the switch has not learned the MAC address of PC3 initially?

<p>PC3 is very quiet in the virtualized environment (D)</p> Signup and view all the answers

When PC1 sends a unicast frame to its default gateway, which of the following is true?

<p>The frame is sent only to the port that connects to the default gateway. (D)</p> Signup and view all the answers

What is the command used by PC3 to display the details of its ethernet adapter?

<p>ifconfig eth0 (D)</p> Signup and view all the answers

What is the purpose of the ARP request sent by PC3?

<p>To request the MAC address of the default gateway (C)</p> Signup and view all the answers

What happens when PC1 sends a broadcast frame into the network?

<p>The switch sends the frame to all ports in the broadcast domain. (D)</p> Signup and view all the answers

Why did the ping to 172.20.5.1 not result in a broadcast?

<p>The ARP cache already had the layer 2 information for the default gateway. (D)</p> Signup and view all the answers

What is the result of the switch learning the MAC address of PC3?

<p>The switch can now forward frames to PC3 using the MAC address (C)</p> Signup and view all the answers

What is the purpose of an ARP request?

<p>To request the layer 2 address of a device. (A)</p> Signup and view all the answers

What is the significance of each port on the switch being its own collision domain?

<p>It allows the switch to reduce collisions on the network (D)</p> Signup and view all the answers

Why did the ping to 172.20.5.99 result in three broadcasts?

<p>The ARP request was sent three times because there was no response. (D)</p> Signup and view all the answers

What is a significant characteristic of a layer 2 switch in terms of broadcast domains?

<p>It combines multiple collision domains into a single broadcast domain. (D)</p> Signup and view all the answers

What happens when the switch receives a frame destined for a MAC address it has learned?

<p>The switch sends the frame to the port associated with the MAC address (A)</p> Signup and view all the answers

What is the primary advantage of a layer 2 switch over a layer 2 bridge?

<p>It reduces the number of collision domains. (C)</p> Signup and view all the answers

Why does the switch not need to send frames to every port when it receives a frame destined for a known MAC address?

<p>Because it has learned the MAC address of the device (B)</p> Signup and view all the answers

What is the result of a switch receiving a frame with an unknown destination MAC address?

<p>The switch sends the frame to all ports in the broadcast domain. (C)</p> Signup and view all the answers

What is an important distinction between layer 2 switching and layer 3 forwarding?

<p>Layer 2 switching uses MAC addresses, while layer 3 forwarding uses IP addresses. (C)</p> Signup and view all the answers

What is the purpose of a layer 2 switch in a network?

<p>To filter traffic based on MAC addresses. (D)</p> Signup and view all the answers

What is the result of capturing traffic on eth0 while sending traffic from PC3?

<p>The capture shows both the ARP request and the ping traffic (A)</p> Signup and view all the answers

What is the result of a device sending a frame with a broadcast destination MAC address?

<p>The switch sends the frame to all ports in the broadcast domain. (D)</p> Signup and view all the answers

What is the role of a layer 2 switch in a network with multiple routers?

<p>It performs layer 2 switching between devices and routers. (D)</p> Signup and view all the answers

Why does the switch learn the MAC address of PC3 when it sends traffic?

<p>Because PC3 sends traffic with its source MAC address (C)</p> Signup and view all the answers

What is a key advantage of using multiple collision domains in a network?

<p>It reduces the number of collisions on the network. (C)</p> Signup and view all the answers

Why did the ping to 172.20.5.50 result in a successful response?

<p>The IP address belonged to another device on the network. (A)</p> Signup and view all the answers

What is true about the devices connected to the switch?

<p>They are part of the same broadcast domain (D)</p> Signup and view all the answers

What happens when a device sends a unicast frame to a MAC address that is not in the switch's MAC address table?

<p>The switch floods the frame to all ports except the one that received it. (D)</p> Signup and view all the answers

What is the primary difference between a layer 2 switch and a layer 2 bridge?

<p>A layer 2 switch provides multiple collision domains, while a layer 2 bridge provides a single collision domain. (A)</p> Signup and view all the answers

What is the effect of a broadcast sent from a device connected to a layer 2 switch?

<p>It is sent to all active ports on the switch. (D)</p> Signup and view all the answers

What is the relationship between layer 2 switching and the forwarding of data between routers?

<p>Layer 2 switching occurs between devices, while forwarding between routers occurs at layer 3. (A)</p> Signup and view all the answers

What is a layer 2 bridge commonly used for?

<p>To connect two segments of a network, creating a single collision domain. (B)</p> Signup and view all the answers

What is the primary benefit of full-duplex communication on a layer 2 switch?

<p>It enables every device to send and receive at the same time. (C)</p> Signup and view all the answers

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Study Notes

Layer 2 Switches

  • A Layer 2 switch makes forwarding decisions based on Layer 2 addresses, specifically Media Access Control (MAC) addresses.
  • A MAC address is 48 bits long, represented by 12 hexadecimal characters, each representing 4 bits.
  • Each network interface card (NIC) has a unique MAC address.

Learning MAC Addresses

  • A Layer 2 switch builds a table of MAC addresses associated with each port.
  • The switch learns MAC addresses by looking at the source MAC address of incoming frames.
  • When a device sends a frame, the switch updates its table with the MAC address and the port it is connected to.

Forwarding Decisions

  • When a switch receives a frame, it checks the destination MAC address and forwards it to the port associated with that MAC address.
  • If the switch doesn't know the MAC address, it forwards the frame to all ports (flooding).
  • A switch can operate in full duplex, allowing devices to send and receive frames simultaneously.

Collision Domains and Broadcast Domains

  • Each port on a switch is its own collision domain, reducing collisions and increasing network efficiency.
  • A switch has one broadcast domain, meaning a broadcast frame is sent to all ports.

ARP Requests

  • An ARP (Address Resolution Protocol) request is a broadcast frame sent to resolve an IP address to a MAC address.
  • The switch forwards ARP requests to all ports in the broadcast domain.
  • The device responding to the ARP request sends a unicast frame with its MAC address, which the switch learns and updates its table.

Switch Configuration and Demonstration

  • A show mac address-table command can be used to display the switch's MAC address table.
  • The switch can be configured to capture packets and display the MAC address table to demonstrate learning and forwarding decisions.
  • A Layer 2 switch with 48 ports would have 48 collision domains and one broadcast domain.### Ping and ARP Request
  • When a ping is sent, it sends an ARP request as a broadcast to find the layer 2 address of the device with the specified IP address
  • The ARP request is sent to all devices on the same broadcast domain, including PC2 and PC3
  • If the IP address is not found, the ping will fail and an ARP request will be sent again

Layer 2 Switching

  • A layer 2 switch is a single broadcast domain, where all devices receive broadcast messages
  • A layer 2 switch forwards broadcast messages to all active ports
  • A layer 2 switch improves upon a layer 2 bridge by giving every device its own collision domain on its own port
  • This allows every device connected to a layer 2 switch to send and receive at the same time, making it full duplex on every port

Layer 2 Bridge

  • A layer 2 bridge is a stepping stone to layer 2 switching, with only a couple of ports
  • A layer 2 bridge divides a single collision domain into multiple collision domains, one for each port

Layer 2 Forwarding

  • Layer 2 forwarding occurs between devices, such as between a PC and a switch, and between switches
  • Layer 2 switching happens between routers, where switches forward data based on layer 2 addresses
  • Layer 2 forwarding is what happens between routers, where switches make forwarding decisions based on layer 2 addresses

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