# Week 1: Subnet Refresher * Dartmouth had hundreds of subnets just in the datacenter * 2^32 IPv4 addresses | 32 bits | Letter | Packet | | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ | |
  1. Look up recipient address

    1. Phone Book? Other Directory?
    2. Get zip code and street address
  3. Put in addressed envelope

    1. Write recipient and return address on envelope
  5. Put letter in mailbox
  6. Mail carrier picks letter up

    1. Take letter to local post office
  8. Post Office sorts and sends to next PO facility

    1. Uses zip code
  10. How does PO know where to send next?

    1. Postal Service has “routing lists”
  12. Ends up at local PO recipient
  13. Mail Carrier delivers to recipient

    1. Uses street address
|
  1. Look up recipient address

    1. Domain Name System (DNS)
    2. Convert Hostname to IP address
  3. Add “Headers” to data (encapsulate)
  4. Send packet to network interface controller (NIC)
  5. Transmits onto network

    1. Sent to local router (AKA default gateway)
  7. Router sends packet to next router

    1. Uses network part of the IP Address
  9. How does the router know where to send next?

    1. “Routing table” of IP networks
  11. Ends up at local router of recipient
  12. Router and switches send to recipient

    1. Uses Host part and IP address and Mac address\`
| * * ^Mailbox ^ Mail server -> translates to ip address TODO: * Download Packet Tracer 8.1.1