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.

1. Phan Bạch Thu ThủyARP (Address Resolution Protocol)5/15/20111

2. Overview5/15/20112WHY?WHERE?WHAT?ARPWHEN?HOW?

3. IntroductionARP is a protocol for mapping an logical address to an physical address.The logical addresses: 32-bit Internet addressPhysical address: 48-bit Ethernet addressWhy address resolution is necessary?5/15/20113

4. ARPARP (address resolution protocol)5/15/20114

5. ARP Operation5/15/20115

6. The Format of ARP packet5/15/20116

7. Position of ARP in TCP/IP Protocol Suite5/15/20117

8. Encapsulation of ARP Packet Encapsulated directly into a data link frame ARP packet encapsulated in an Ethernet frame5/15/20118

9. Cases using ARPCase 2. A host wants to send a packet to another host on another network. It must first be delivered to the default router.5/15/20119

10. Cases using ARP (cont.)5/15/201110

11. ExampleMAC A.B.C.1.3.3MACff.ff.ff.ff.ff.ffIP197.15.22.33IP197.15.22.35What is your MAC Addr?197.15.22.33197.15.22.35197.15.22.34A.B.C.1.3.3A.B.C.7.3.5A.B.C.4.3.4ABC5/15/201111

12. Example (Cont.)MAC A.B.C.1.3.3MACff.ff.ff.ff.ff.ffIP197.15.22.33IP197.15.22.35What is your MAC Addr?197.15.22.33197.15.22.35197.15.22.34A.B.C.1.3.3A.B.C.7.3.5A.B.C.4.3.4ABCThat is my IP !5/15/201112

13. Example (Cont.)MAC A.B.C.7.3.5MACA.B.C.1.3.3IP197.15.22.35IP197.15.22.33I am the node you’re looking forThis is my MAC Addr197.15.22.33197.15.22.35197.15.22.34A.B.C.1.3.3A.B.C.7.3.5A.B.C.4.3.4ABC ARP Reply5/15/201113

14. Example (Cont.)MAC A.B.C.1.3.3MACA.B.C.7.3.5IP197.15.22.33IP197.15.22.35Data197.15.22.33197.15.22.35197.15.22.34A.B.C.1.3.3A.B.C.7.3.5A.B.C.4.3.4ABCARP Table:A.B.C.7.3.5 – 197.15.22.355/15/201114

15. SummaryARP is Address resolution protocol.ARP request and ARP reply.Format of ARP packet.Encapsulation of ARP packet.Cases using ARP.5/15/201115