What is the function of a default gateway?

• A. The next-hop router to reach destinations outside the local network
• B. The DNS server for name resolution
• C. A device that translates private IPs to public IPs
• D. A host's local switch

Answer: (A)

The function of a default gateway is to provide the exit path from a local network to destinations outside of that network. When a device wants to reach an address that isn’t on its own subnet, it cannot send the packet directly to the destination. Instead, it forwards the packet to the gateway, which is the next-hop router on the local network. The gateway has a route for non-local destinations (often configured as a default route like 0.0.0.0/0) and knows how to forward the packet toward other networks, possibly across multiple routers until it reaches the destination.

If the destination is on the same local network, the device can send directly (using ARP to map the IP to a MAC address) and no gateway is involved. NAT is a common function some gateways perform, translating private IP addresses to a public address for internet access, but the essential role of the default gateway is simply to route traffic to destinations outside the local subnet.