Addressing

Addressing

1. Physical addresses

   • Hardware address
     • Non-resetable
     • Burned into each network interface at the factory
     • MAC address
       • 48-bit
       • Media Access Control
   • Layer 2

2. Logical addresses

   • IP address
     • IPv4 address
       • 4 bytes or 32 bits

3. Address resolution protocol

   • When contacting a node with it's logical address...
     • ARP converts it to it's hardware address
   • Cache
     • Maps previously discovered IP addresses to MAC addresses

4. ARP steps

   • 1. Check ARP cache for destination's MAC address, if found, use it
   • 2. Source broadcasts ARP request to entire LAN asking for the MAC address
   • 3. Each node checks if IP address belongs to it
   • 4. If it doesn't own IP address, it ignores the request
   • 5. Destination send ARP reply with own hardware address to source
   • 6. Source stores destination's hardware address in ARP cache