IP addressing and MAC addressing

1.3.2 Wired and wireless networks, protocols and layers

Wired and wireless networks, protocols and layers — Note 3 of 13

What you need to know

IP addresses and MAC addresses both identify endpoints in networking, but they answer different questions. A MAC address identifies built-in hardware on a LAN; an IP address identifies logical location on a network and is used when traffic is routed between networks.

What to know

MAC: 48 bits total: 6 groups of 2 hex digits, often shown with colons or hyphens. First part identifies the manufacturer (OUI); the rest is unique to the device.
IP: Logical address: must be unique on the network segment you are using at that moment, but the same device can get a different IP on a different network or after renewal if using DHCP.
IPv4 addresses are 32-bit: four decimal numbers separated by dots (e.g. 192.168.1.1).
IPv6 addresses are 128-bit: eight groups of four hexadecimal digits separated by colons.

Key terms

MAC Addressseparate idea: A unique identifier built into the device's network hardware (NIC), assigned by the manufacturer. Written in hexadecimal (e.g. 00:1A:2B:3C:4D:5E). Used for communication within a local network (LAN). It does not change — it is a permanent hardware address (burned into the NIC).
IP Addressseparate idea: Assigned to a device on a network to identify its logical location on that network. Can be static (fixed) or dynamic (can change over time or when reconnecting, e.g. via DHCP). Used for routing and for communication between networks — routers use the destination IP to decide the path.

Exam technique

Tip:LAN delivery to a specific NIC is tied to MAC (switching). Getting traffic across the Internet between networks is tied to IP (routing).
Tip:Key difference — IP addresses can CHANGE (especially dynamic IPs); MAC addresses are fixed at manufacture for the NIC.
Mistake:Saying MAC addresses can be changed by the user like an IP. For GCSE purposes they are built-in and do not change.
Mistake:Saying the router 'sends to the correct MAC' for everything on your Wi-Fi. The router routes using IP between networks; your combined home box also contains switching/Wi-Fi that delivers frames to MAC addresses on the LAN.
Tip:IPv4 = 4 groups of 0-255 separated by DOTS. IPv6 = 8 groups of hex separated by COLONS. Common error: giving 6 groups for IPv6 or using dots instead of colons.

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