6. DHCP Request and Acknowledge

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Summary Table for the DHCP Request

Layer Information Checked Other DHCP Servers The Chosen Router
Data Link MAC: FF:FF:FF:FF:FF:FF (usually) "I'll listen to this broadcast." "I'll listen to this broadcast."
Network IP: 255.255.255.255 "I'll keep reading." "I'll keep reading."
Transport Port: 67 "Checking my offers..." "Checking my offers..."
Application Requested IP & Server ID "They didn't choose me. I'll take back my IP offer." They want my IP! Time to send the ACK."

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Summary Table: How the Client Processes the DHCP ACK

Layer Information Checked Other Devices (Phones, etc.) The Client (Your Computer)
Data Link MAC: FF:FF:FF:FF:FF:FF "Broadcast, I'll take it." "Broadcast, I'll take it."
Network IP: 255.255.255.255 "Broadcast, keep reading." "Broadcast, keep reading."
Transport Port: 68 "Not my traffic. DROP." "I am the Client. ACCEPT."
Application DHCP Message Type: ACK (Already dropped) "Confirmation received! I am now 192.168.1.10!"

Notes:

  • Client IP is updated only after processing ACK.
  • Lease Time tells how long the IP is valid.
  • APIPA (169.254.x.x) is replaced by router-assigned IP.