First-hand · verified against the real thing
The printer that goes offline every few days: the fixed IP is the whole story
In one line: DHCP re-leases, the router reservation that ends them, the Windows port re-point nobody knows exists, and why 'restart everything' only clears this week's episode.
A wireless printer is a computer with a grudge: your laptop talks to it by its network address, and the router reissues that address like a taxi rank reallocating cabs. Every lease renewal can hand the printer a new number while the laptop keeps calling the old one - the printer prints nothing, screams "offline", and the restart ritual you have learned "fixes" it, right up until next Tuesday. The permanent cure is one configuration step on the router and, on Windows, one field in the printer properties. Here they are.
Step one: give the printer a number that never changes
Print the network configuration page (the menu calls it Wireless/Network - Print Test Page; the printer's current IP is on it, which you should note down anyway). Then log into the router - the gateway address is on that same page - and find DHCP reservations (Address Reservation / Static Lease, named by the brand). Reserve the printer's current IP to its MAC address, save. The printer now reboots back into the same address forever, and the lease churn stops being anyone's problem. Do the same on your laptop's end - a fixed address for the printer, not for the laptop; this is the printer's reservation.
Step two: Windows' port, the part almost nobody re-points
- Control Panel - Devices and Printers - your printer - Printer properties - Ports. More often than not the port is a WSD port ("Web Services for Devices"), and WSD is the discovery layer that keeps mis-remembering the printer - it is the technical name for the problem. Add a port instead: Standard TCP/IP Printer Port, New Port, type in the reserved IP; leave the defaults from there. Windows now talks numbers, not guesses.
- On the printer itself, turn off deep sleep if the menu offers it - some brands' power-saving modes drop the Wi-Fi radio and the "offline" state returns through a different door.
- Mac and CUPS: add the queue by its protocol address (AirPrint for simple jobs, IPP/LPR pointed at the same reserved IP) and it resolves like Windows' TCP port, not Bonjour drift.
When it is not the IP, by process of elimination
The reserved-IP-and-TCP-port fix works on a well-behaved printer; the list of what a remaining offline pattern actually was on real desks, in order of how cheaply you can test each: the printer and the laptop on different networks - guest bands, or the router's 2.4/5GHz split putting the printer on a separate SSID the laptop never sees; a band-steering router that keeps re-docking the printer to 5GHz the office never routes to - put the printer on the 2.4GHz SSID alone and name it; the router's AP isolation turned on (blocks devices seeing each other - printing and scanning both die at once, which is the tell); the HP Smart/Epson Connect apps re-adding a "cloud" queue that shadows the real one (delete every duplicate printer in the list until one remains, then re-test); and finally the printer's own Wi-Fi radio failing weakly - one ethernet cable to the router ends that debate and the printer's licence to complain.
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