Fundamentals
MAC address vs. IP address: what's the difference?
Both identify a device on a network. Neither does the other one's job, and mixing them up is the source of a lot of confused troubleshooting.
The short version: a MAC address identifies a network interface, permanently (or as close to it as the hardware allows); an IP address identifies where that interface currently is on a network, and changes depending on the answer. One is closer to a name, the other closer to a postal address that changes when you move.
| MAC address | IP address | |
|---|---|---|
| Layer | Data link (Layer 2) | Network (Layer 3) |
| Assigned by | The hardware vendor (or software, if randomized/locally administered) | DHCP, or configured manually |
| Format | 48 bits, e.g. 28:6F:B9:00:00:00 | 32 bits (IPv4) or 128 bits (IPv6), e.g. 192.168.1.42 |
| Scope | Meaningful within one local network segment | Meaningful for routing across networks, including the internet |
| Changes when... | Rarely; only if spoofed, randomized, or the hardware is replaced | Routinely; a new network, a DHCP lease renewal, a VPN connecting |
How they work together
On a local network, delivering a packet to a given IP address still ultimately means putting a frame on the wire addressed to a MAC address. ARP (Address Resolution Protocol) is the glue: a device broadcasts "who has this IP address," the owner replies with its MAC address, and the sender caches that mapping to address frames directly from then on. That's also exactly why a MAC address, not an IP, is what your router's "connected devices" list and any switch's forwarding table actually key off of, IP addresses come and go, but within one session the MAC address is the stable handle for "this specific interface."
IPv6 goes a step further and can derive part of a device's own address directly from its MAC address (a "modified EUI-64" interface identifier), rather than treating the two as unrelated. Our lookup tool shows this derivation for any address you enter.
Want the deeper structural breakdown of the MAC address half of this comparison? See how MAC addresses are structured.
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