1.3.1. Physical vs. Logical Addressing

MAC Address (Layer 2):

• Burned into hardware at manufacturing
• 48 bits: 00:1A:2B:3C:4D:5E
• Identifies a specific network interface card
• Used for delivery within a single network segment
• Changes hop-by-hop as frames traverse routers

IP Address (Layer 3):

• Assigned by configuration (static or DHCP)
• IPv4: 32 bits (192.168.1.1), IPv6: 128 bits
• Identifies network location, not physical hardware
• Used for end-to-end delivery across networks
• Stays the same from source to destination

ARP (Address Resolution Protocol): Bridges the gap between IP and MAC. When a device knows the destination IP but needs the MAC, it broadcasts: "Who has 10.0.0.1?" The owner responds with its MAC. This is why "ARP table" questions appear on the exam—it's the mechanism that connects Layer 3 to Layer 2.