Why IP address instead of MAC address ?


At first glance, this question feels almost unnecessary.

Both IP addresses and MAC addresses are unique identifiers.
So why do we use IP addresses for communication across networks instead of MAC addresses?

That curiosity pushed me to revisit some networking fundamentals — and the answer turns out to be surprisingly elegant.

What Is a MAC Address?

A MAC (Media Access Control) address is a unique hexadecimal identifier assigned to a network interface by the manufacturer.

Key properties:

  • Assigned at manufacturing time

  • Works at the Data Link Layer (Layer 2)

  • Intended for local network communication

  • Flat addressing (no hierarchy)

Although often called “hardcoded,” modern systems can spoof or change MAC addresses — but logically, they are still hardware-level identifiers.

What Is an IP Address?

An IP (Internet Protocol) address is a logical identifier assigned by:

  • a network administrator, or

  • automatically via DHCP

Key properties:

  • Works at the Network Layer (Layer 3)

  • Can change when the device moves networks

  • Hierarchical and structured

  • Designed for routing across networks

The Key Difference: Logical Structure

Let’s look at an example IP address:

192.168.1.10

This address isn’t random. It has structure.

In simple terms:

  • 192.168.1 → Network portion

  • 10 → Host within that network

(The exact split depends on subnetting, but the idea remains the same.)

This structure is what makes IP powerful.

Routers don’t need to know every device on Earth.
They only need to know which network an IP belongs to and where to forward the packet next.

Why MAC Addresses Can’t Scale

MAC addresses have no built-in hierarchy.

They don’t tell you:

  • which network a device belongs to

  • how far away it is

  • which router should handle it next

If we tried to route traffic using MAC addresses:

  • every router would need to track billions of MAC addresses

  • routing tables would become unmanageable

  • global networking would collapse under its own weight

MAC addressing works beautifully — inside a local network.
That’s exactly where it’s meant to operate.

Why IP Addresses Work Globally

IP addresses solve this problem through logical grouping.

Routers don’t care about individual devices at first.
They care about:

  • network prefixes

  • routing paths between networks

For example:

  • an IP block like 142.250.0.0/16 tells routers “this traffic belongs to a specific network”

  • the router forwards the packet closer to that network

  • only at the destination network does MAC addressing come back into play

This layered approach is what allows the internet to scale.

How Both Actually Work Together

It’s not IP vs MAC.

It’s IP + MAC, each doing its own job:

  • IP address → gets the packet to the correct network

  • MAC address → delivers the packet to the correct device inside that network

Routing uses IP.
Local delivery uses MAC.

That separation is intentional — and powerful.

Final Thought

The reason we use IP addresses instead of MAC addresses for routing isn’t because MAC addresses are bad.

It’s because:

MAC addresses are local by design.
IP addresses are global by design.

And the internet only works because we respect that boundary. 



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