A host sends a packet to a web server on a remote network. Which statement correctly distinguishes the destination Internet Protocol (IP) address from the destination Media Access Control (MAC) address in the first Ethernet frame?

### Why this is right The IP destination identifies where the packet is ultimately meant to go. Because the server is remote, the host sends the first frame to its local next hop, usually the default gateway, so the frame's destination MAC address belongs to that gateway. ### The concept An IP packet carries network-layer source and destination addresses used to move traffic across networks. An Ethernet frame carries link-layer MAC addresses for delivery over one local link. When a router forwards a packet, it removes the incoming Ethernet header and creates a new one for the next link, so the MAC destination changes hop by hop. The IP destination normally stays the same across those hops, except when Network Address Translation (NAT) changes an address. | Address | Identifies | Typical behavior across routers | |---|---|---| | IP address | The packet's network destination | Remains the end destination unless translated | | MAC address | The next physical hop on a local link | Replaced for each new link | ### The other options - **B. The destination IP address identifies the next switch, while the destination MAC address identifies the ultimate server.**: This reverses the jobs of the two addresses. Switches forward using MAC addresses, while IP addresses identify network destinations. - **C. Both addresses identify the ultimate server and remain unchanged at every router.**: This is true of neither address in this scenario. The MAC destination changes at each routed hop, and the first MAC destination is the gateway, not the remote server. - **D. The destination MAC address identifies the remote network, while the destination IP address identifies the local gateway.**: This reverses both roles. The IP address identifies the remote destination, and the local frame is addressed to the gateway's MAC address. ### Terms - **IP**: Internet Protocol. It provides addresses used to deliver packets across networks. - **MAC**: Media Access Control. The link-layer addressing scheme used to deliver Ethernet frames on a local link. - **Ethernet frame**: A unit of data sent over an Ethernet link, with a header that includes source and destination MAC addresses. - **Default gateway**: The local router or routing interface a host uses to reach another network. - **Router**: A device that forwards packets between networks using IP destinations. - **Switch**: A device that forwards local frames using MAC addresses. - **NAT**: Network Address Translation. A process that changes an IP address as traffic passes through a device. ### Remember The IP address points to the packet's ultimate destination; the MAC address points to the next local hop.