What is the purpose of the default route 0.0.0.0 in routing tables?

• A. Used when the destination network is unknown
• B. Used to broadcast to all hosts
• C. Maps DNS to IP
• D. Identifies the loopback

Answer: (A)

A default route acts as a catch-all path for destinations that don’t have a specific route in the table. The entry 0.0.0.0/0 says that any destination not matched by a more precise route should be forwarded to the configured next-hop gateway, which is how a router forwards traffic toward networks it doesn’t know about locally (often toward the internet).

Routing relies on the longest prefix match, so more specific routes take precedence. If a destination isn’t covered by those, the default route handles it. The other concepts mentioned—broadcast to all hosts, DNS-to-IP mapping, and the loopback address—are not used to forward packets to external networks.