Which IP address range is designated to indicate the default route?

• A. 0.0.0.0
• B. 255.0.0.0
• C. 127.0.0.1
• D. 10.0.0.0

Answer: (A)

Think of a default route as the last-resort path for any destination. In IPv4 routing, the entry that covers every possible address is the destination 0.0.0.0 with a mask of 0.0.0.0 (often written as 0.0.0.0/0). The 0.0.0.0 destination means “any address,” so this rule directs packets to the default gateway when there isn’t a more specific route for where the packet should go. That’s why this address range is used to indicate the default route.

The other options don’t serve this purpose: 255.0.0.0 is a subnet mask, not a destination for routing; 127.0.0.1 is the loopback address used to reach the local host; 10.0.0.0 is a private address block used within a local network, not a universal catch-all for routing.