Table of Contents
MAC Address
A MAC (Media Access Control) address is a unique identifier assigned to a network interface.
Unlike an IP address, which identifies a device's location on a network, a MAC address identifies the network hardware itself.
MAC addresses are used for communication within the same local network (LAN).
MAC Address Format
A MAC address consists of 48 bits (6 bytes).
It is usually written as six hexadecimal numbers separated by colons or hyphens.
Example:
00:1A:2B:3C:4D:5E
or
00-1A-2B-3C-4D-5E
Each pair represents one byte.
Why Do We Need MAC Addresses?
Devices on the same local network communicate using MAC addresses.
For example:
Computer A 192.168.1.10 ↓ MAC 00:1A:2B:3C:4D:5E ↓ Ethernet ↓ Computer B 192.168.1.20
Although applications usually use IP addresses, the actual Ethernet frames delivered across a LAN contain MAC addresses.
MAC Address vs IP Address
| MAC Address | IP Address |
|---|---|
| Identifies a network interface | Identifies a network location |
| Layer 2 (Data Link Layer) | Layer 3 (Network Layer) |
| Used inside a LAN | Used between networks |
| Normally permanent | May change |
A packet sent over an Ethernet network contains both MAC addresses and IP addresses.
How Does a Computer Find a MAC Address?
Suppose a computer wants to send data to:
192.168.1.20
It first determines whether the destination is on the same subnet.
If it is, the operating system uses ARP (Address Resolution Protocol) to discover the destination MAC address.
Example:
Who has 192.168.1.20 ? ↓ Response MAC A4:83:E7:12:34:56
The computer can then send the Ethernet frame to the correct device.
MAC Addresses and Routers
MAC addresses are not routed across the Internet.
Each router replaces the source and destination MAC addresses before forwarding a packet to the next network.
Therefore:
- IP addresses usually remain the same.
- MAC addresses change at every router.
Can a MAC Address Change?
The hardware MAC address is assigned by the manufacturer.
However, many operating systems allow the MAC address to be temporarily changed.
This is known as:
- MAC Spoofing
- MAC Randomization
Modern smartphones often randomize their MAC address when connecting to Wi-Fi networks to improve privacy.
Is a MAC Address Globally Unique?
Manufacturers receive an OUI (Organizationally Unique Identifier) from the IEEE.
The first three bytes identify the manufacturer.
Example:
00:1A:2B ↓ Manufacturer
The remaining bytes identify the specific network interface.
Although MAC addresses are intended to be unique, duplicates may exist due to configuration errors or spoofing.
Broadcast MAC Address
Ethernet defines one special broadcast address:
FF:FF:FF:FF:FF:FF
Frames sent to this address are delivered to every device on the local network.
MAC Addresses and Telenegar
Current Telenegar tools do not use MAC addresses because they operate over the Internet.
MAC addresses are only visible within the local network and are not transmitted across routers.
For this reason, Telenegar tools such as:
cannot determine the MAC address of a remote device.
Common Misconceptions
- A MAC address is the same as an IP address.
- False. They serve different purposes.
- A website can see my MAC address.
- False. MAC addresses are never transmitted across the Internet.
- Changing a MAC address changes my public IP address.
- False. These are unrelated.