Does an IP address identify a particular device?¶
title: "Does an IP address identify a particular device?" card_id: "IP-061" status: "complete" source_document: "https://docs.google.com/document/d/1-jiSZRo42FSDCfI2DHxVSsG950h_8vIJ2znTq1iosTE/edit?usp=drivesdk"
Does an IP address identify a particular device?¶
An IP address is sometimes described as the address of a device.
That is useful as a basic explanation, but it can become misleading very quickly.
An IP address identifies where network traffic can be sent or where it appeared to come from at a particular observation point.
It doesn't normally act as a permanent serial number for one device.
A laptop connected to a home Wi-Fi network may have a private IP address assigned by the router. If the laptop leaves that network and connects at work, in a hotel or through a mobile hotspot, it will receive a different address.
Even on the same network, its private address may change when the router makes a new allocation.
When the laptop communicates across the internet, the service it contacts will normally see the household’s public IP address—not the laptop’s private address.
Every device using that router may appear to come from the same public address because NAT translates their traffic.
The same public address could therefore represent a laptop, phone, television, games console or any other connected device inside the property.
CGNAT can extend that sharing further by allowing several different customers to use the same public IP address.
IPv6 doesn't turn the address into a permanent device identifier either. A device can hold several IPv6 addresses and may generate temporary addresses intended to reduce long-term tracking.
The position of the recording system also matters.
A router inside a workplace may record a private address that relates to one device on that local network. An external platform may record a public address representing the organisation’s shared internet connection.
Those records describe the same communication from different observation points.
An IP address can still be important evidence.
Combined with an exact timestamp and the appropriate provider or local-network records, it may help identify a subscriber connection, network session or locally connected device.
But each of those is a separate step.
An IP address doesn't, by itself, permanently identify a physical device. It identifies an address being used within a particular network context at a particular time.