Address Resolution Protocol (ARP) Overview
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Questions and Answers

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

  • To facilitate NIC to NIC communications on the same network. (correct)
  • To identify devices for IP address resolution.
  • To send messages across different networks.
  • To route packets to remote networks.

    • When a host knows the IP address but not the MAC address of the destination device, what process is utilized?

  • Packet encapsulation.
  • IP address resolution.
  • Address resolution. (correct)
  • Routing.

    • In the scenario where a destination IP address is on the same network, how is the MAC address determined?

  • It is retrieved from the IP address database.
  • It is the same as the source MAC address.
  • It is obtained from the destination device. (correct)
  • It is the address of the default gateway.

    • What MAC address will a host use to send a packet to a destination on a remote network?

    <p>The MAC address of the local default gateway.</p> Signup and view all the answers

    Which layer does the MAC address operate at within the OSI model?

    <p>Layer 2 - Data Link Layer.</p> Signup and view all the answers

    What does a router do upon receiving an Ethernet frame?

    <p>It de-encapsulates the Layer 2 information.</p> Signup and view all the answers

    Why is the logical address important in packet switching?

    <p>It allows routers to determine the best path for packet forwarding.</p> Signup and view all the answers

    How does the destination MAC address differ when sending packets to a remote network compared to the same network?

    <p>It refers to the local default gateway instead of the destination device.</p> Signup and view all the answers

    What happens if no device responds to an ARP request?

    <p>The packet is dropped because a frame cannot be created.</p> Signup and view all the answers

    How long do ARP entries typically last in newer Windows operating systems?

    <p>15 to 45 seconds</p> Signup and view all the answers

    What command is used on a Cisco router to display the ARP table?

    <p>show ip arp</p> Signup and view all the answers

    What type of ARP entries do not expire over time?

    <p>Static ARP entries</p> Signup and view all the answers

    What is a potential security risk associated with ARP?

    <p>ARP spoofing</p> Signup and view all the answers

    What must a source device do when the destination IPv4 address is on another network?

    <p>Send the frame to its default gateway.</p> Signup and view all the answers

    Which IPv6 messages are used for address resolution?

    <p>Neighbor Solicitation and Neighbor Advertisement</p> Signup and view all the answers

    What is the primary purpose of the Address Resolution Protocol (ARP)?

    <p>To map IPv4 addresses to MAC addresses</p> Signup and view all the answers

    What action may be taken to remove an entry from the ARP table?

    <p>Manually use a command to remove it</p> Signup and view all the answers

    Which of the following is NOT part of the ICMPv6 Neighbor Discovery protocol?

    <p>ARP Request</p> Signup and view all the answers

    When a device cannot find a MAC address for an IPv4 address in its ARP table, what does it initiate?

    <p>An ARP request</p> Signup and view all the answers

    What technique is used by threat actors to manipulate ARP entries?

    <p>ARP spoofing</p> Signup and view all the answers

    What information is not included in the ARP request frame?

    <p>IPv4 header</p> Signup and view all the answers

    How does a device determine its next-hop MAC address for a packet destined for another network?

    <p>By looking up the MAC address of the default gateway in the ARP table</p> Signup and view all the answers

    What occurs to an ARP entry if the device does not receive a frame before the timestamp expires?

    <p>The entry is removed from the ARP table.</p> Signup and view all the answers

    What does each entry in the ARP table bind together?

    <p>IPv4 addresses and their corresponding MAC addresses</p> Signup and view all the answers

    What is one advantage of using dynamic ARP inspection (DAI) in networks?

    <p>Mitigates ARP spoofing attacks</p> Signup and view all the answers

    What happens to ARP requests sent on the network?

    <p>They are broadcast to all devices on the LAN.</p> Signup and view all the answers

    Which message in ICMPv6 is used for router discovery?

    <p>Router Advertisement</p> Signup and view all the answers

    Which process must occur again after an ARP entry has been removed?

    <p>Sending an ARP request and receiving an ARP reply</p> Signup and view all the answers

    What type of address does the destination MAC address in an ARP request represent?

    <p>A broadcast address</p> Signup and view all the answers

    After sending an ARP request, what will the device do when it receives an ARP reply?

    <p>It will update its ARP table with the new MAC address.</p> Signup and view all the answers

    Which layer encapsulates the IPv4 packet in a new data link frame?

    <p>Data Link layer</p> Signup and view all the answers

    What is maintained in the ARP cache?

    <p>Currently active IPv4 to MAC address mappings</p> Signup and view all the answers

    Which protocol is used for mac address discovery in IPv6 networks?

    <p>ICMPv6 Neighbor Discovery</p> Signup and view all the answers

    What will the device do if it cannot find the IPv4 address in the ARP cache?

    <p>Send a broadcast ARP request</p> Signup and view all the answers

    What does an ARP table entry consist of?

    <p>A mapping of an IPv4 address to its corresponding MAC address</p> Signup and view all the answers

    Study Notes

    Address Resolution Protocol (ARP)

    • ARP Function: ARP is a protocol responsible for mapping IPv4 addresses to MAC addresses on an Ethernet network.
    • ARP Table: Each device on an Ethernet network maintains an ARP table (or ARP cache) to store temporary mappings between IPv4 addresses and MAC addresses.
    • ARP Operation: When a device needs to send a packet to a destination on the same network, it first checks its ARP table for the destination's MAC address.
      • If the MAC address is found: The device uses the corresponding MAC address to create an Ethernet frame.
      • If the MAC address is not found: The device broadcasts an ARP request to all devices on the network, inquiring about the MAC address corresponding to the destination's IPv4 address.
      • ARP Reply: The device with the destination IPv4 address responds with an ARP reply containing its MAC address.
    • ARP Entry Removal: ARP entries are time-stamped and expire after a predetermined period of inactivity. Entries can also be removed manually.
    • ARP Issues:
      • ARP Broadcasts: ARP requests are broadcasted, which can slightly impact network performance during high network usage.
      • ARP Spoofing: Threat actors can use ARP spoofing to redirect network traffic to themselves by sending fake ARP replies with their own MAC address.

    IPv6 Neighbor Discovery (ND)

    • ND Function: ND is similar to ARP for IPv6, providing address resolution, router discovery, and redirection services.
    • ND Messages: ND uses five ICMPv6 messages for its services:
      • Neighbor Solicitation: Sent to discover the MAC address of a device with a known IPv6 address.
      • Neighbor Advertisement: Sent in response to a Neighbor Solicitation to provide the requesting device with its own MAC address.
      • Router Solicitation: Sent to discover the presence of routers on the IPv6 network.
      • Router Advertisement: Sent by routers to respond to Router Solicitations and advertise their own information.
      • Redirect Message: Used for better next-hop selection (beyond the scope of this summary).
    • ND Address Resolution: ND uses Neighbor Solicitation and Neighbor Advertisement messages to resolve MAC addresses for known IPv6 addresses in a similar way that ARP does for IPv4.

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    Description

    This quiz covers the essentials of the Address Resolution Protocol (ARP), including its function, operation, and how ARP tables are maintained. Test your knowledge on how devices map IPv4 addresses to MAC addresses and the process involved in ARP requests and replies.

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