ARP (Address Resolution Protocol) maps logical IP addresses to physical MAC addresses. It works by broadcasting an ARP request packet containing the logical IP address, and the physical host with that IP will respond with its MAC address in an ARP reply packet. ARP packets are encapsulated within Ethernet frames to be transmitted at the data link layer, and ARP is used to resolve addresses both for hosts on the same local network and for traffic destined for a default router on another network.
3. Introduction ARP is a protocol for mapping an logical address to an physical address. The logical addresses: 32-bit Internet address Physical address: 48-bit Ethernet address Why address resolution is necessary? 5/15/2011 3
8. Encapsulation of ARP Packet Encapsulated directly into a data link frame ARP packet encapsulated in an Ethernet frame 5/15/2011 8
9. Cases using ARP Case 2. A host wants to send a packet to another host on another network. It must first be delivered to the default router. 5/15/2011 9
11. Example MAC A.B.C.1.3.3 MAC ff.ff.ff.ff.ff.ff IP 197.15.22.33 IP 197.15.22.35 What is your MAC Addr? 197.15.22.33 197.15.22.35 197.15.22.34 A.B.C.1.3.3 A.B.C.7.3.5 A.B.C.4.3.4 A B C 5/15/2011 11
12. Example (Cont.) MAC A.B.C.1.3.3 MAC ff.ff.ff.ff.ff.ff IP 197.15.22.33 IP 197.15.22.35 What is your MAC Addr? 197.15.22.33 197.15.22.35 197.15.22.34 A.B.C.1.3.3 A.B.C.7.3.5 A.B.C.4.3.4 A B C That is my IP ! 5/15/2011 12
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14. Example (Cont.) MAC A.B.C.1.3.3 MAC A.B.C.7.3.5 IP 197.15.22.33 IP 197.15.22.35 Data 197.15.22.33 197.15.22.35 197.15.22.34 A.B.C.1.3.3 A.B.C.7.3.5 A.B.C.4.3.4 A B C ARP Table: A.B.C.7.3.5 – 197.15.22.35 5/15/2011 14
15. Summary ARP is Address resolution protocol. ARP request and ARP reply. Format of ARP packet. Encapsulation of ARP packet. Cases using ARP. 5/15/2011 15
