A host at `172.16.10.3/24` sends a packet to `172.16.20.111`. Explain how the host determines that the destination is outside its subnet, where it sends the packet first, and the difference between the destination Internet Protocol (IP) address and destination Ethernet address.

### Why this is right With a `/24` mask, the first three octets identify the subnet. The sender is on `172.16.10.0/24`, while the destination is on `172.16.20.0/24`, so the host must use a router. The destination IP continues to identify the ultimate destination; the Ethernet destination identifies the next hop on the local link. ### The concept A host uses its IP address and subnet mask to decide whether another address is local. A local destination can be reached within the subnet through switching. A remote destination is sent to the **default gateway**, the router that accepts traffic for destinations outside the local subnet. The router then forwards the packet toward the remote network using the destination IP. Ethernet addresses apply to a local link and can change at each routed hop, whereas the end-to-end IP destination identifies where the packet is ultimately going. ### What a good answer covers - The sender's subnet is `172.16.10.0/24`. - The destination is in a different subnet, `172.16.20.0/24`. - The host sends the packet to its default gateway. - The IP destination is the remote host, while the Ethernet destination is the local router. ### Terms - **IP**: Internet Protocol. It provides logical addressing used to move packets between networks. - **Ethernet**: A local networking technology that carries frames between devices on a link. - **Default gateway**: The router a host uses to reach destinations outside its own subnet. - **Subnet mask**: A value that lets a host distinguish local network bits from host bits. ### Remember For remote traffic, the IP address points to the final destination and the Ethernet address points to the next local hop.