NETWORK
MAC addressHardware addresses on the local link
A MAC address is the 48-bit hardware identifier of a network interface, written as six hex pairs such as A4-5E-60-1B-2C-3D. It is used to deliver frames on the local network segment (Ethernet or Wi-Fi) and does not travel beyond the first router. The first three pairs identify the manufacturer.
What a MAC address is for
IP addresses route packets across networks; MAC addresses deliver frames across a single link. When your PC sends a packet to the default gateway, the IP header carries the final destination (say a web server) but the Ethernet frame carries the router's MAC address as its destination. The router strips that frame, builds a new one for the next link, and so on. Your MAC never leaves the local segment.
Devices learn the MAC that corresponds to an IP through ARP (IPv4) or Neighbour Discovery (IPv6).
Format
A4-5E-60-1B-2C-3D
└──OUI──┘ └─NIC──┘- The OUI (first three bytes) is registered to the manufacturer with IEEE. Looking it up tells you a device is an Apple, Intel or Raspberry Pi product, which is useful for identifying unknown devices in a DHCP table.
- The second-lowest bit of the first byte is the locally administered flag. If it is set (first byte x2, x6, xA or xE), the address was chosen by software, not assigned by a manufacturer. Randomised and virtual-machine MACs use this.
- Some tools show 64-bit EUI-64 identifiers, which IPv6 SLAAC once derived from MACs by inserting
FF-FEin the middle; modern systems use random identifiers instead.
Where MAC addresses are used
- Switching: switches learn which MAC is on which port and forward frames accordingly.
- DHCP reservations tie a fixed IP to a MAC. See static vs dynamic IP.
- MAC filtering on Wi-Fi: weak as a security control (addresses are trivially spoofed) but occasionally used for convenience.
- 802.1X and RADIUS (port 1812) can authenticate devices by MAC as a fallback ("MAC authentication bypass").
- Wake-on-LAN sends a magic packet containing the target's MAC.
Finding it on Windows
ipconfig /all
getmac /vipconfig /all lists each adapter's Physical Address. getmac /v gives a compact table with the adapter name and transport. In PowerShell, Get-NetAdapter shows the same as MacAddress.
Randomisation
Windows 11 (Settings → Wi-Fi → Random hardware addresses), Android 10+ and iOS 14+ can present a different MAC to each Wi-Fi network. This defeats tracking by shops and hotspot operators. It also breaks anything that keys on the MAC: reservations, captive-portal sessions, parental controls. Turn it off for your home network if you use those features, and leave it on for public networks.
Frequently asked questions
Is a MAC address unique?
Manufacturers assign each interface a unique address from their IEEE-registered block, so in principle yes. In practice, virtual machines, cloned devices and randomisation features mean duplicates can occur, which only matters on the same local segment.
Can a MAC address be tracked on the internet?
No. Frames carry the MAC of the next hop, not the original sender, so a website never sees your MAC. It is visible to the local network (the café Wi-Fi, for instance), which is why phones randomise it per network.
Why does my phone show a different MAC on each Wi-Fi network?
iOS, Android and Windows 10/11 support per-network random MAC addresses to prevent tracking across locations. Devices with a DHCP reservation or MAC filter need the feature turned off for that network.