What happens when a router receives a packet?

• A. It examines the destination address and then uses the routing table to find the best path
• B. It immediately forwards to the local interface
• C. It encrypts the payload
• D. It queries the DNS

Answer: (A)

When a router receives a packet, the core action is to decide where to send it next. It does this by looking at the destination IP address inside the packet and consulting its routing table to find the best path toward that destination. The routing table lists networks, masks, and the next-hop or exit interface, and the router uses a longest-prefix match to pick the most specific route. Once a route is chosen, the router forwards the packet to the next hop (or directly to the appropriate connected network) and may use ARP to learn the next-hop MAC address. It may also decrement the TTL to prevent loops and handle any access control rules or QoS as configured. This is why examining the destination address and using the routing table to determine the next hop is the essential, correct behavior.

En route, a router does not simply forward to the local interface without considering the destination, nor does it encrypt the payload or query DNS as part of basic forwarding.