What is the difference between Source IP and Destination IP in an IPv4 packet?

• A. Source IP is the sender's address; Destination IP is the intended recipient's address.
• B. Source IP is the receiver's address; Destination IP is the sender's.
• C. Source IP is used for routing; Destination IP is for DNS.
• D. Source and Destination are always the same.

Answer: (A)

Any IPv4 packet carries two addresses in its header: the Source IP and the Destination IP. The Source IP is the sender’s address—the device that created and sent the packet. The Destination IP is the intended recipient’s address—the device the packet should reach. Routers use the Destination IP to decide where to forward the packet next, so it can reach the final destination. The Source IP is useful for the recipient to know where the packet came from, enabling replies and helping with logging, troubleshooting, and security checks. DNS, which maps domain names to IPs, operates at a higher level and isn’t what directs the routing of the packet; the Destination IP is not a DNS field. So the difference is that the Source IP identifies who sent the packet, while the Destination IP identifies who should receive it.