What does 0.0.0.0/0 represent in routing?

• A. A local network
• B. An invalid route
• C. An address reserved for multicast
• D. Default route that matches any destination not covered by more specific routes

Answer: (D)

In routing, the key idea is how destinations are matched against routes. The entry 0.0.0.0/0 acts as the default route, a catch-all path. The subnet mask of 0 bits means it matches any IPv4 address, so it’s used when there isn’t a more specific route for a destination. The router forwards traffic that doesn’t match any other route to the next hop specified by this default route (often toward the internet or an upstream gateway). More specific routes take precedence, so a precise network like a local subnet will be chosen over the default route. The other options don’t fit because 0.0.0.0/0 isn’t a local network, isn’t invalid, and isn’t a multicast address; it’s the broad, all-encompassing route used to reach destinations that aren’t explicitly known to the routing table.