On a single IP network, why must each device have a different IP address, even though they share the same network prefix?

Introduction / Context:
In IP networking, every device connected to a given logical network segment must have a unique IP address within that segment. Devices on the same network share a common network prefix, but the host portion of the address must be different for each one. This question explores why uniqueness of IP addresses is essential for correct communication.

Given Data / Assumptions:

• Devices on a local network, such as computers and printers, use IP addresses to communicate.
• They share a subnet defined by a network prefix and subnet mask.
• Routers and switches rely on these addresses to deliver packets.

Concept / Approach:
An IP address has two parts: a network part that identifies the network and a host part that identifies the specific device on that network. If two devices on the same network had exactly the same IP address, the network would not be able to distinguish between them. Packets sent to that address could be delivered to the wrong device or not delivered reliably at all. Unique IP addresses ensure that addressing and routing mechanisms, including ARP on IPv4 networks, can map each IP address to a unique hardware address and deliver data correctly.

Step-by-Step Solution:
Step 1: Remember that IP addresses are used to identify both the network and the host.Step 2: On a given subnet, the network portion is the same for all devices, but the host portion must be unique.Step 3: Consider what happens if two devices share the same IP address: ARP tables and routing tables become inconsistent, and packets may be misdelivered.Step 4: Understand that unique addresses allow routers and switches to maintain clear mappings between IP addresses and physical ports or MAC addresses.Step 5: Select the option that explains uniqueness in terms of correct delivery and avoiding conflicts.

Verification / Alternative check:
Practical experience confirms this. If you misconfigure two computers with the same IP address on a local network, you often see address conflict warnings, intermittent connectivity, and failed pings. Network diagnostic tools show ARP table entries changing back and forth as each device responds. When each device has a different IP address, these problems disappear and communication becomes stable, confirming the need for unique host addresses.

Why Other Options Are Wrong:
Option B: Talks about physical cable length and signal loss, which are unrelated to logical IP address assignment.Option C: Suggests sharing the same MAC address, which is also problematic; both IP and MAC addresses must be unique within the broadcast domain.Option D: Claims that uniqueness is required so that only one computer can ever join, which is opposite to the purpose of networking multiple devices.

Common Pitfalls:
Some learners confuse network prefixes and host addresses and think that entire IP addresses must be completely different without understanding the shared network portion. Others underestimate the impact of address conflicts and think that minor overlaps are acceptable. In reality, even one duplicate IP address can cause serious connectivity issues on a local subnet.

Final Answer:
The correct answer is To uniquely identify each host so that routers and switches can deliver packets to the correct destination without address conflicts.