5. DHCP Offer

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  1. Application Layer:

    • Contains assigned IP (192.168.1.10), subnet mask, gateway (192.168.1.1)
    • Includes client MAC (chaddr) so the client knows the offer is for it

  2. Transport Layer:

    • Source Port 67: The Router (Server).
    • Destination Port 68: The Computer (Client).

  3. Network:

    • Source IP: 192.168.1.1 router’s LAN IP (gateway)
    • Destination IP: 255.255.255.255 (broadcast ip, because the client has no IP yet)

  4. Data Link Layer (MAC)

    • Source MAC: A1:B1:C1:D1:E1:F1
    • Destination MAC: Broadcast (FF:FF:FF:FF:FF:FF)

  5. Physical Layer & NIC

    • NIC converts frame to electrical/wireless signals and sent on network.

Broadcast ensures delivery to clients without IP; chaddr + xid ensures correct matching.

Summary Table: How the Client Processes the DHCP Offer

Layer Information Checked Other Devices (Phones, etc.) The Client (Your Computer)
Data Link MAC: FF:FF:FF:FF:FF:FF "It's a broadcast, I'll take it." "It's a broadcast, I'll take it."
Network IP: 255.255.255.255 "It's a broadcast, keep going." "It's a broadcast, keep going."
Transport Port: 68 "I'm not looking for an IP. DROP." "I am waiting for an IP! ACCEPT."
Application chaddr: A:B:C:D:E:F (Already dropped at Transport) "That's MY MAC address! This is MY offer!"