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Address Resolution Protocol (ARP)

Address Resolution Protocol (ARP). 1A-2F-BB-76-09-AD. LAN (wired or wireless). 71-65-F7-2B-08-53. 58-23-D7-FA-20-B0. 0C-C4-11-6F-E3-98. LAN Addresses and ARP. Each adapter on LAN has unique LAN address. Broadcast address = FF-FF-FF-FF-FF-FF. = adapter. LAN Address (more).

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Address Resolution Protocol (ARP)

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  1. Address Resolution Protocol(ARP)

  2. 1A-2F-BB-76-09-AD LAN (wired or wireless) 71-65-F7-2B-08-53 58-23-D7-FA-20-B0 0C-C4-11-6F-E3-98 LAN Addresses and ARP Each adapter on LAN has unique LAN address Broadcast address = FF-FF-FF-FF-FF-FF = adapter

  3. LAN Address (more) • MAC address allocation administered by IEEE • manufacturer buys portion of MAC address space (to assure uniqueness) • Analogy: • MAC address: like Social Security Number • IP address: like postal address • MAC flat address ➜ portability • can move LAN card from one LAN to another • IP hierarchical address NOT portable • depends on IP subnet to which node is attached

  4. IP Address 0 23 24 31 • IP address format Network ID Host ID • Multicast Address • 224.0.0.0 to 239.255.255.255 • Private address • 10.0.0.0 ~ 10.255.255.255 (10/8 prefix) • 172.16.0.0 ~172.31.255.255 (172.16/12 prefix) • 192.168.0.0 ~ 192.168.255.255 (192.168/16 prefix) • Special address

  5. data CRC type 6 6 2 64-1500 4 dst src

  6. IP Address/Physical Address • Static Mapping • IP broadcast address maps to Ethernet broadcast address) • IP Multicast Address maps to Ethernet Multicast Address • lower 23bits of class D IP map into the lower 23bits of Ethernet address 01:00:5e:00:00:00 • Dynamic Mapping • ARP • RARP

  7. ARP • Address Resolution Protocol • RFC-826 • Mapping between IP address and the physical address(such as MAC)

  8. ARP/RARP Packet Format 0 16 31 proto type hard type HLEN op PLEN sender ethernet address sender ether addr sender IP addr target ether addr sender IP addr target ethernet address target IP address Hardware type = 1 : Ethernet Protocol type = 080016: IP address HLEN: hardware address length = 6 : Ethernet MAC address length PLEN: protocol address length = 4 : IP address length OP(operation): 1: ARP request, 2: ARP response, 3: RARP request, 4: RARP response

  9. How it works ? To :140.113.25.6  ‚ ARP IP … ƒ Ethernet † (broadcast) „ Ethernet Ethernet ARP ARP IP 140.113.25.6

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