Ethernet Frames and MAC Sublayer
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Questions and Answers

What is the primary function of the MAC sublayer?

  • To manage network topology
  • To provide physical layer technologies
  • To provide error detection
  • To encapsulate data and access media (correct)

    • What is the purpose of the frame check sequence (FCS) trailer in an Ethernet frame?

  • To provide source and destination MAC addresses
  • To ensure error-free transmission
  • To detect errors and correct them
  • To detect errors (correct)

    • What type of access method is used in half-duplex Ethernet?

  • Round-robin
  • Polling
  • Carrier sense multiple access/collision detection (CSMA/CD) (correct)
  • Token passing

    • What is the benefit of using switches in modern Ethernet LANs?

    <p>They do not require access control through CSMA/CD</p> Signup and view all the answers

    What is the purpose of the back-off algorithm in CSMA/CD?

    <p>To retransmit data</p> Signup and view all the answers

    What type of medium is used in legacy Ethernet?

    <p>Half-duplex</p> Signup and view all the answers

    What is the purpose of the source and destination MAC addresses in an Ethernet frame?

    <p>To deliver the Ethernet frame from one device to another</p> Signup and view all the answers

    What is the type of topology used in legacy Ethernet?

    <p>Bus topology</p> Signup and view all the answers

    What type of device will have an Ethernet NIC and a MAC address?

    <p>Any device that is the source or destination of an Ethernet frame</p> Signup and view all the answers

    What is the purpose of a unicast MAC address in Ethernet?

    <p>To send a frame from a single transmitting device to a single destination device</p> Signup and view all the answers

    What is the process used to determine the destination MAC address associated with an IPv4 address?

    <p>Address Resolution Protocol (ARP)</p> Signup and view all the answers

    What is the destination MAC address of an Ethernet broadcast frame?

    <p>FF-FF-FF-FF-FF-FF</p> Signup and view all the answers

    How does an Ethernet switch handle an Ethernet broadcast frame?

    <p>It floods the frame out all ports including the incoming port</p> Signup and view all the answers

    What happens to an Ethernet broadcast frame when it reaches a router?

    <p>It is not forwarded</p> Signup and view all the answers

    What is the significance of the destination IPv4 address in an Ethernet broadcast frame?

    <p>It has all ones in the host portion</p> Signup and view all the answers

    What is the purpose of the source MAC address in an Ethernet frame?

    <p>To identify the source device</p> Signup and view all the answers

    What does a switch use to make forwarding decisions?

    <p>MAC addresses</p> Signup and view all the answers

    What happens when a switch is turned on?

    <p>The MAC address table is empty</p> Signup and view all the answers

    What does a switch do when it receives a frame with a new source MAC address?

    <p>It adds the MAC address to the table</p> Signup and view all the answers

    What happens to an entry in the MAC address table after 5 minutes?

    <p>The entry is deleted</p> Signup and view all the answers

    What happens when a switch receives a frame with a source MAC address that exists in the table but on a different port?

    <p>The switch treats it as a new entry</p> Signup and view all the answers

    What does a switch do when it receives a frame with a unicast destination MAC address?

    <p>It looks for a match in its MAC address table</p> Signup and view all the answers

    What is the MAC address table also referred to as?

    <p>CAM table</p> Signup and view all the answers

    What is the purpose of the switch examining the source MAC address of the frame?

    <p>To learn new information</p> Signup and view all the answers

    What happens when a switch receives a frame with a destination MAC address that is not in its table?

    <p>The switch forwards the frame out all ports except the incoming port.</p> Signup and view all the answers

    How does a switch populate its MAC address table?

    <p>By examining the source MAC address of every frame.</p> Signup and view all the answers

    What is the advantage of store-and-forward switching?

    <p>It determines if a frame has errors before propagating the frame.</p> Signup and view all the answers

    How many forwarding methods are used by Cisco switches?

    <p>Two</p> Signup and view all the answers

    What happens when a switch receives a broadcast or multicast frame?

    <p>The switch forwards the frame out all ports except the incoming port.</p> Signup and view all the answers

    What is the minimum requirement for the cut-through switching method?

    <p>At least the destination address must be read.</p> Signup and view all the answers

    What happens when a switch's MAC address table contains the destination MAC address?

    <p>The switch forwards the frame out a single port.</p> Signup and view all the answers

    What is the purpose of computing the CRC in store-and-forward switching?

    <p>To determine if the frame has errors.</p> Signup and view all the answers

    What should be the configuration of autonegotiation on both sides of a link?

    <p>Both sides on</p> Signup and view all the answers

    What is the best practice for configuring Ethernet switch ports?

    <p>Configure them as full-duplex</p> Signup and view all the answers

    What type of connection requires a cross-over cable?

    <p>A connection between a router and a host</p> Signup and view all the answers

    What is the purpose of the auto-MDIX feature?

    <p>To automatically detect the type of cable attached to the port</p> Signup and view all the answers

    What should you always use when connecting devices?

    <p>The correct type of cable</p> Signup and view all the answers

    What is the default state of the auto-MDIX feature on switches running Cisco IOS Release 12.2(18)SE or later?

    <p>Enabled</p> Signup and view all the answers

    How can you re-enable the auto-MDIX feature?

    <p>Using the 'mdix auto' command</p> Signup and view all the answers

    What is the reason for not relying on the auto-MDIX feature?

    <p>It can be disabled</p> Signup and view all the answers

    What is the length of an Ethernet MAC address in bytes?

    <p>6 bytes</p> Signup and view all the answers

    What is the purpose of the organizationally unique identifier (OUI) in an Ethernet MAC address?

    <p>To identify the device's manufacturer</p> Signup and view all the answers

    What happens when a NIC receives an Ethernet frame with a destination MAC address that does not match its own?

    <p>The NIC discards the frame</p> Signup and view all the answers

    What type of MAC address is an Ethernet NIC configured to accept?

    <p>Unicast, broadcast, and multicast MAC addresses</p> Signup and view all the answers

    What is the significance of the source MAC address in an Ethernet frame?

    <p>It identifies the source device</p> Signup and view all the answers

    What is the purpose of the MAC address in an Ethernet LAN?

    <p>To provide device identification at the data link layer</p> Signup and view all the answers

    How many hexadecimal digits are used to express an Ethernet MAC address?

    <p>12 hexadecimal digits</p> Signup and view all the answers

    Why must all Ethernet devices have unique MAC addresses?

    <p>To ensure device identification at the data link layer</p> Signup and view all the answers

    What is the primary function of the LLC sublayer in Ethernet?

    <p>Communicating between the networking software and the device hardware</p> Signup and view all the answers

    What is the advantage of using Ethernet technology in LANs?

    <p>It supports bandwidths of up to 100 Gbps</p> Signup and view all the answers

    What is the purpose of the MAC sublayer in Ethernet?

    <p>Data encapsulation and media access control</p> Signup and view all the answers

    What is the main difference between Ethernet and WLANs?

    <p>Ethernet uses wired connections while WLANs use wireless connections</p> Signup and view all the answers

    What is the purpose of the Ethernet frame?

    <p>To encapsulate data for transmission over a network</p> Signup and view all the answers

    Which standard defines the Layer 2 protocols and Layer 1 technologies used in Ethernet?

    <p>IEEE 802.2 and 802.3</p> Signup and view all the answers

    What is the primary function of the data link layer in Ethernet?

    <p>To encapsulate data for transmission over a network</p> Signup and view all the answers

    What is the advantage of using multiple Layer 3 protocols on the same network interface and media?

    <p>It enables the use of multiple Layer 3 protocols, such as IPv4 and IPv6</p> Signup and view all the answers

    What does a switch do with the source MAC address of a frame when it is not in the MAC address table?

    <p>It adds the source MAC address to the table along with the incoming port number.</p> Signup and view all the answers

    What happens to an entry in the MAC address table if the source MAC address exists in the table but on a different port?

    <p>The entry is updated with the new port number.</p> Signup and view all the answers

    How does a switch make forwarding decisions?

    <p>Based on Layer 2 Ethernet MAC addresses</p> Signup and view all the answers

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

    <p>To filter out erroneous frames and forward them to the correct port</p> Signup and view all the answers

    What is the default time for which an entry stays in the MAC address table?

    <p>5 minutes</p> Signup and view all the answers

    What is the purpose of a switch examining the source MAC address of every frame?

    <p>To populate its MAC address table</p> Signup and view all the answers

    What does a switch do when it receives a frame with a unicast destination MAC address?

    <p>It looks for a match between the destination MAC address and an entry in its MAC address table.</p> Signup and view all the answers

    What happens when a switch receives a frame with a destination MAC address that is not in its table?

    <p>It forwards the frame out all ports except the incoming port</p> Signup and view all the answers

    What is the MAC address table also referred to as?

    <p>Content addressable memory (CAM) table</p> Signup and view all the answers

    How does a switch learn new MAC addresses?

    <p>By examining the source MAC address of incoming frames</p> Signup and view all the answers

    What is the advantage of using cut-through switching over store-and-forward switching?

    <p>It forwards the frame before it is entirely received</p> Signup and view all the answers

    What is the purpose of an unknown unicast in a switch?

    <p>To forward frames to all ports except the incoming port</p> Signup and view all the answers

    What happens when a switch receives a frame with a destination MAC address that is not in its table?

    <p>It broadcasts the frame to all ports.</p> Signup and view all the answers

    What is the difference between store-and-forward switching and cut-through switching?

    <p>Store-and-forward switching receives the entire frame before forwarding, while cut-through switching forwards the frame before it is entirely received</p> Signup and view all the answers

    What happens when a switch receives a frame with a broadcast or multicast destination MAC address?

    <p>It forwards the frame out all ports except the incoming port</p> Signup and view all the answers

    What is the benefit of using store-and-forward switching over cut-through switching?

    <p>It determines if a frame has errors before propagating the frame</p> Signup and view all the answers

    What happens when an error is detected in a frame?

    <p>The switch discards the frame.</p> Signup and view all the answers

    What is the primary purpose of store-and-forward switching?

    <p>To analyze quality of service (QoS) on converged networks</p> Signup and view all the answers

    What is the key difference between fast-forward switching and other cut-through switching methods?

    <p>It has lower latency due to immediate forwarding</p> Signup and view all the answers

    What happens to faulty packets in fast-forward switching?

    <p>They are relayed to the destination NIC, which discards them</p> Signup and view all the answers

    Why is store-and-forward switching required for converged networks?

    <p>To analyze quality of service (QoS) for traffic prioritization</p> Signup and view all the answers

    How does a switch determine the port to forward data in cut-through switching?

    <p>By buffering just enough of the frame to read the destination MAC address</p> Signup and view all the answers

    What is the primary advantage of cut-through switching over store-and-forward switching?

    <p>Lower latency due to immediate forwarding</p> Signup and view all the answers

    What is the typical cut-through switching method of switching?

    <p>Fast-forward switching</p> Signup and view all the answers

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