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ARP

Address Resolution Protocol

  • ARP Lives in the ,Data Link Layer and **Network Link Layer
  • Arp Sends out message "Who has mac address for x.y.z.a and if you know about it, send it back to me"
  • Allow us to get a mac address of another devices on the network.
  • Devices on the network will maintain an ARP cahce
    • list of ip address to mac address association
    • Arp age out cache every 90s, so arp will have to re-resolve ip to mac address every
    • Switched do not need ARP tables
    • You can't ARP address that is not on your local network. 
      1
      show ip route # show avaliable routes on default gw.