MAC and IP Addresses: Two Different Jobs

Networks use several kinds of identifiers.

Two that beginners often confuse are MAC addresses and IP addresses.

They are related to communication, but they solve different problems.

MAC address concept

A network interface can have a link-layer hardware address commonly represented in hexadecimal, for example:

00:1A:2B:3C:4D:5E

In a local Ethernet-style network, this kind of address helps frames reach interfaces on the local link.

Do not treat a MAC address as a permanent identity for a person. Interfaces can change, addresses can be randomized or configured, and devices may have multiple interfaces.

IP address concept

An IP address identifies a network-layer location used for routing packets.

IPv4 addresses are commonly written as four decimal octets:

192.0.2.25

Each octet represents an 8-bit value from 0 to 255.

That connects directly to Week 10.

Convert an IPv4 octet

Take decimal 192.

In 8-bit binary:

11000000

Take decimal 25:

00011001

An IPv4 address can therefore be understood as four groups of eight bits even though humans normally write decimal notation.

IPv4 and IPv6

IPv4 uses 32-bit addresses.

IPv6 uses a much larger address space and is commonly written using hexadecimal groups separated by colons.

Example documentation-style IPv6 address:

2001:db8::25

For this course, you do not need advanced IPv6 routing. Recognize the notation and understand that IPv4 and IPv6 are network-layer addressing systems.

Local identifier versus routed identifier

Use a conceptual delivery model:

• IP tells the network where the packet is trying to go across network boundaries
• local link delivery uses the appropriate local interface addressing

This is why one device can appear with both an IP address and a MAC address in a local capture.

Addressing lab

Use only teacher-provided documentation addresses.

For these IPv4 values:

• 192.0.2.5
• 198.51.100.42
• 203.0.113.200

Choose one octet from each and convert it to 8-bit binary and hex.

Basic subnet idea

A subnet groups addresses into a network range.

At this introductory level, focus on the idea that part of an address identifies the network and part identifies a host/interface within that network.

Your teacher may provide a simple /24 example where the first three IPv4 octets are treated as the network portion.

Example:

192.0.2.0/24

Possible host addresses in that classroom example share the 192.0.2 network prefix.

Do not scan or probe any real network range.

Build an address card

For a fictional workstation, create:

• MAC address from teacher-provided sample
• IPv4 address
• IPv6 address
• local subnet
• default router address from the synthetic scenario

Then explain what each value helps the network do.

Misconception check

Evaluate:

"MAC address and IP address are two names for the same device."

Incorrect. They operate at different layers and have different roles.

"If I know an IP address, I know who the person is."

Incorrect. An address identifies network configuration/location, not automatically a human identity.

"Every number in an IPv4 address can be 0–999."

Incorrect. Each written octet represents an 8-bit value from 0 through 255.

Evidence for Lesson 2

Submit:

• IPv4 octet conversion table
• fictional address card
• simple subnet explanation
• misconception corrections

Finish with:

An IP address helps routing because ________, while a MAC address helps local delivery because ________.