Routing Between Networks

Layer 3 handles communication between different networks. This is where IP addresses and routing decisions happen.

Key concepts:

• IP addresses — assigned by administrators, define network membership
• Routers — forward packets between networks based on destination IP
• Subnet masks — determine if traffic stays local or needs routing
• Default gateway — your path to other networks

The Key Distinction

Same subnet = Layer 2 (switching). Different subnet = Layer 3 (routing).