Written 27 Aug 2026. This is a how-to, not a product card. Buy links are not tagged yet.

See the leftover box's hardware address

Before you reserve the leftover box's number, write down the sticker-like address the router uses to recognize it.

The hardware address (MAC) is a sticker-like number on the network plug. It stays put when the house number (IP) moves. The router uses it to pick this leftover box out of the client list. You already know the leftover box's house number from see the leftover box's address on the house network. This note writes down the sticker so keep the leftover box on the same number is easy.

Skip until SSH works

If you have never logged in from the couch, that is SSH from the couch. You can also type this at the leftover-box keyboard. Prefer this look after a cable is plugged in, ping to the router works, and you know the cable speed: a cable beats Wi-Fi for the leftover box, then check that the leftover box can reach the house router, then see how fast the leftover-box cable is talking. This note assumes you can log in from the couch, or sit at the leftover-box keyboard.

What this is

A look, not a shopping trip. You need this sticker to reserve the leftover box's number on the house router. Do not buy a switch for a hardware address. The same command already told you the cable was UP in a cable beats Wi-Fi for the leftover box. This time, copy the six pairs.

Ask for the sticker

SSH in from the couch, or sit at the leftover-box keyboard, then ask:

ip -br link

Skip the lo line. That is the leftover box talking to itself. Point at the ethernet line that is UP (often a name that starts with en, or eth0). The six pairs with colons are the hardware address. Copy that one. Wi-Fi lines can wait if a cable is plugged in.

Optional longer print

If you want the longer table:

ip link show

Point at the same UP ethernet name. The link/ether line is the same sticker. Keep this light. Do not change the address tonight.

Write it down

Sticky note or phone, next to the house number from see the leftover box's address on the house network. The next step is keep the leftover box on the same number. Match this sticker on the router client list so the reservation sticks to this leftover box, not a phone that borrowed the old number.

What next

Keep the number stable: keep the leftover box on the same number. Cable speed: see how fast the leftover-box cable is talking. Path to the router: check that the leftover box can reach the house router. Cable: a cable beats Wi-Fi for the leftover box.

Skip

• Skip if SSH and the leftover-box keyboard both fail. That is is the leftover box still on? or SSH from the couch.
• Skip a new switch for this look.
• Skip typing a static IP into Linux on the leftover box. The reservation on the router is enough.
• Skip forwarding port 22.
• Skip buying a NAS for a sticker.
• Skip Proxmox tonight. That is what a VM is, and when you do not need one.