Computer networksLesson 1 of 1 in the course Link and physical layer

ARP: Address Resolution, Caching, and Related Protocols

5 flashcards · 5 quiz questions · 5 match pairs · 5 fill-in sentences · English

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Summary

Address Resolution Protocol (ARP) lets a device on an IPv4 local network find the link-layer address, usually a MAC address, associated with an IPv4 address. This lesson introduces ARP's purpose, operating scope, and message format.

An IP packet is addressed using an internet-layer address, such as an IPv4 address. To send that packet over a local Ethernet link, the sender also needs the destination's Ethernet MAC address. ARP discovers the required mapping between these addresses.

All flashcards

What is ARP?
Address Resolution Protocol discovers a link-layer address, usually a MAC address, associated with an internet-layer address such as an IPv4 address.
Why does an IPv4 host use ARP on Ethernet?
The host needs the destination or next-hop MAC address to create an Ethernet frame carrying its IP packet.
Where do ARP messages operate?
They operate within one local subnetwork and are carried directly by a link-layer protocol; they are not routed.
What is the difference between EtherType 0x0806 and PTYPE 0x0800?
EtherType 0x0806 identifies an ARP payload in the Ethernet frame. PTYPE 0x0800, inside the ARP message, identifies IPv4 as the protocol whose addresses are being resolved.
What provides neighbor resolution in IPv6?
Neighbor Discovery Protocol (NDP) provides the corresponding neighbor-resolution functionality in IPv6 networks.

Quiz questions

  1. When a node's data-link address is already known, what does Inverse ARP (InARP) discover?Answer: The network-layer address of that node.
  2. What was Reverse ARP (RARP) designed to let a device obtain?Answer: Its own network-layer address, using its link-layer address.
  3. A system answers ARP requests on behalf of another system and forwards traffic for it. What is this behavior called?Answer: Proxy ARP.
  4. What field values characterize an ARP probe used to check a proposed IPv4 address?Answer: SPA and THA are zero, and TPA contains the candidate address.
  5. What is the purpose of a gratuitous ARP announcement?Answer: To inform local hosts about an address mapping without seeking a reply.

Based on the Wikipedia article Address Resolution Protocol, licensed CC BY-SA 4.0. Adapted into a summary, flashcards and quizzes.

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