What is a default gateway and why is it essential for remote network communication?

The default gateway is the router interface IP on the local LAN — the "door" to all remote networks; without it configured, a host's traffic is confined to its own LAN.

* Off-LAN traffic goes to the default gateway, which forwards it onward. *

The default gateway is the router interface IP address that is part of the local LAN.

Why it's essential:

• When the destination is on a different network (remote), the source cannot send directly
• The source must send the frame to the default gateway (router) first
• The router then forwards the packet toward the final destination

Key points:

• All devices on the LAN must know the default gateway address
• Without a default gateway configured, traffic will be confined to the local LAN only
• The default gateway is the "door" to all other remote networks

Go deeper:

• Default gateway — the "router of last resort" for traffic with no specific route.
• Host to Host through a Router — Practical Networking — what the gateway does once it receives off-LAN traffic.