A home network device inventory: an observation table behind every row, and the MAC address as an observation rather than a key

Goal

Keep a list of what is connected to the home network that survives a device being renamed, getting a new IP lease or presenting a different MAC address, and that records when each device was seen rather than what someone believes is there.

Prerequisites

Access to the router's client or DHCP lease list, or a computer on the network on which ip neigh can be run; its manual page notes that the IPv4 neighbour table is also known by another name, the ARP table, so it shows only neighbours whose link-layer address the computer has resolved recently, not every device on the network. The identifier's limits: Apple's support page explains that a device identifies itself to a Wi-Fi network by a unique network address called a Media Access Control (MAC) address and that its Private Wi-Fi Address feature exists so that one address is not used across all networks; Android's documentation describes persistent and non-persistent MAC randomisation and states that if the user disables it, the factory MAC address is used. A spreadsheet with a device table and a separate observation table.

Steps

1. Device table: household name ("kitchen tablet"), type, owner or room, make and model, a printed identifier if any (serial number, label), and the row's creation date.
2. Observation table, appended and never edited: date and time, source (router list, ip neigh, a phone app), MAC address as shown, hostname as shown, IP address, connection (wired, or Wi-Fi band if displayed), and the device row it was matched to, or "unmatched".
3. Match an observation to a device by hostname, by the time it appeared, or by switching the device off and seeing which entry goes stale; record the matching rule in its own column.
4. Take a snapshot weekly and after events: a new device, a guest, a router restart, an OS update.
5. Derive first-seen and last-seen per device from the observation table, never by hand.
6. Keep unmatched observations as rows; after two unmatched snapshots mark them "unidentified" rather than deleting them.

Expected result

A device list whose every attribute traces back to a dated observation, in which a MAC address change on a phone appears as two observations matched to one device, and in which unmatched entries stay visible with their dates.

Limits and test basis

Proposed protocol; nothing is claimed about how many devices a home has or how often addresses change. A device that is off, asleep or on another band may be absent from a snapshot, so "last seen" is a lower bound. The inventory records; it does not judge whether a device belongs, block anything or change router settings, and is not a security control.