When a PC sends a packet to another PC in a remote network, what destination IP address and destination MAC address are placed in the Ethernet frame that the PC sends to its default gateway?

Introduction / Context:
Understanding how IP and MAC addressing interact is a core networking concept. When a host communicates with a device on a different IP subnet, it must use its default gateway to reach that remote network. This question asks you to identify which destination IP and MAC addresses are placed in the first Ethernet frame that the sending PC forwards to its default gateway.

Given Data / Assumptions:

• PC A is the source and PC B is the destination, and they are on different IP subnets.
• PC A has a configured default gateway on the local router interface.
• The network uses Ethernet at Layer 2 and IP at Layer 3.
• ARP is available for resolving local MAC addresses, and routing is configured on the gateway.

Concept / Approach:
In IP networking, the destination IP in the packet remains the IP address of the final destination host (PC B) for the entire journey. However, the destination MAC address in each Ethernet frame is only needed for delivery to the next hop on the local link. When PC A sends traffic to a remote network, the next hop is the default gateway router interface. Therefore, PC A uses ARP to discover the MAC address of the gateway and places that address in the frame header, even though the IP packet inside is addressed to PC B.

Step-by-Step Solution:
Step 1: PC A checks its IP address and subnet mask and determines that the destination IP address of PC B is on a different subnet.Step 2: PC A decides to send the packet to its default gateway, which will route the packet toward the remote subnet.Step 3: To build the Ethernet frame, PC A needs the MAC address of the default gateway interface on the local network.Step 4: PC A sends an ARP request asking for the MAC address corresponding to the default gateway IP address and receives the ARP reply with the router interface MAC.Step 5: PC A constructs an Ethernet frame with destination MAC set to the router interface MAC and source MAC set to its own MAC, while the encapsulated IP packet has destination IP equal to the IP address of PC B.

Verification / Alternative check:
By capturing packets on the local LAN with a tool such as Wireshark, you can confirm that frames sent from a host to a remote network have the router MAC as the destination MAC, but the IP destination remains the remote host. As packets cross each router, the MAC addresses are rewritten for the new next hop, but the IP addresses stay constant end to end.

Why Other Options Are Wrong:
Option A incorrectly claims that the destination IP is the default gateway IP; in reality, the destination IP is the remote host.Option C incorrectly uses the broadcast MAC address for normal unicast traffic; broadcast is only used for discovery such as ARP, not for every packet.Option D sets the destination IP to the gateway and destination MAC to the local PC, which is not how unicast forwarding works.Option E uses the network address as an IP destination and a switch MAC at Layer 2, neither of which is correct for unicast host to host communication.

Common Pitfalls:
Many learners mistakenly think that the IP packet is addressed to the default gateway instead of to the final destination, or they confuse which MAC address is used on each hop. Remember that IP destination stays as the final host, while the destination MAC address always belongs to the next hop device on the current link.

Final Answer:
The frame sent to the default gateway uses Destination IP as the remote PC IP address and destination MAC as the MAC address of the default gateway interface.