What it means
Ethernet and Wi-Fi interfaces use these addresses for local frame delivery. A device may have different addresses for different interfaces or wireless networks. Privacy features can rotate Wi-Fi addresses. Router reservations or access lists that rely on an old address may therefore stop matching.
How this affects everyday use
Replacing an adapter, using a dock or enabling a private address can create what appears to be a new client. MAC filtering alone is weak access control because addresses are observable and can be imitated.
A practical example
A phone reconnects with a private address, so a reservation tied to its previous address no longer applies.
What to check
- Inspect the address of the interface actually in use.
- Compare the router's current client list and reservation.
- Check the device's per-network privacy setting.
Practical next steps
- Update an authorised reservation to match the intended configuration.
- Prefer supported authentication rather than MAC-only protection.
- Retain privacy addressing where compatible with the network.
Keeping it reliable
Document why any exception is required and avoid disabling privacy globally. An address list is inventory assistance, not a dependable record of who used the connection.