The Whole House Went Offline After a New Router
Why this matters
The call comes in as "your thermostat is broken." It is not broken. On Monday the internet provider swapped the customer's old gateway for a new one, and by Tuesday the thermostat, the water shutoff, the doorbell, the sprinkler controller, the garage opener and the camera recorder all read offline. To the customer it looks like everything you installed failed at once. To you it is one change in the house that broke three different things, and if you fix only the first, you leave with half the house still dark and a return visit nobody wants to pay for.
This is one case, worked through in order: the fix that was right, why it was not enough, and the two other changes hiding behind it.
The call and what the tech knew before arriving
The customer's message: everything connected says offline, the internet itself works (they can stream video and their phones are fine), and the provider replaced the router "a couple of days ago."
That last phrase is most of the diagnosis. When every connected device in a house fails at the same moment and the internet works, the shared cause is almost always the network the devices join, not the devices. Eight devices do not fail independently on the same day.
The tech pulled the device records from the shop's history before leaving. They listed eight networked devices, all on a network named ORTIZ-HOME, 2.4 GHz, and one note on the camera recorder: "NVR set to static address 192.168.1.50 at install." That note turned out to matter more than anything else on the cards.
Change one: a new network name and password
A replacement router comes out of the box broadcasting its own network name and password, printed on its label. Every device in the house was still trying to join ORTIZ-HOME with the old password, which no longer existed. That alone takes everything offline.
There are two ways to fix it.
Re-join every device to the new network. Some devices make this easy (a menu on the thermostat), some require a factory reset and a full re-setup through their app (garage openers and doorbells often do), and some need the original installer's account to re-onboard. Across eight devices, an hour or more, and a reset device can lose its schedules and settings.
Give the new router the old name and password. Change the new router's network name to ORTIZ-HOME and its password to the old one, exactly, capitals included. Devices that were retrying the old credentials find a network that answers to them and rejoin on their own.
The second is faster by a wide margin, and it is a change to the customer's router, which needs the customer's explicit permission and, where the provider owns and manages the unit, may not be possible from the customer's side at all. See related: The Customer Network Change Authorization SOP. Mrs. Ortiz authorized it. The old password was on a sticker on the old gateway, which she had photographed before the provider took it away.
Ten minutes after the rename, five of the eight devices were back online: the thermostat, the water shutoff hub, the doorbell, and both smart plugs.
The diagnosis was right, and three devices were still dark. This is the point where a tech who stops at "it was the router" leaves the job unfinished.
Change two: the band and security settings
The old gateway had broadcast two network names: ORTIZ-HOME on 2.4 GHz and ORTIZ-HOME-5G on 5 GHz. The new router broadcast one name for both bands and let it steer each device to a band (called band steering). It also defaulted to a security mode that offers both WPA2 and the newer WPA3 (a "transition" or mixed mode).
Most current 2.4 GHz devices handle both of those without noticing. Some older devices do not: a combined-band name or a mixed security mode can stop them joining, with the device showing only "cannot connect" or a blinking light. Which devices are affected varies by device age and firmware and is not something to guess; the test is whether changing the setting brings the device back.
The sprinkler controller was the oldest device in the house, installed six years ago. The tech, with Mrs. Ortiz's permission, set the router's security mode to WPA2 only and power-cycled the controller at its outlet in the garage. It joined within 2 minutes.
That fix carries a tradeoff the customer should hear. WPA2 is still widely used and acceptable, but it is the older standard, and setting the whole network to it to suit one device lowers the network's ceiling. The alternative is a separate 2.4 GHz network for the old devices, if the router supports one, or replacing the controller. The tech wrote the tradeoff on the ticket and recommended replacing the controller at its next service, so the network can go back to the mixed mode.
The garage opener: right credentials, stale attempt
The garage opener's module was the one device the rename should have fixed and did not. Its app still read offline after 20 minutes.
Some devices that fail to join a network repeatedly back off and retry less and less often, sometimes not for hours. The fix is a power cycle. The opener plugs into a ceiling outlet; the tech closed the door fully first, set a stepladder to the side of the opener rail rather than under the door's path, unplugged the head for 30 seconds and plugged it back in. Within 3 minutes the module joined ORTIZ-HOME and the app showed it online. The tech then ran the door one full cycle from the app with Mrs. Ortiz watching from inside, then ran the reversal test the opener manual gives (a board laid flat in the door path on a close, plus a box pushed through the photo-eye beam during a close, never a hand or foot) to confirm the door reversed both times, because power-cycling the head is the kind of act after which you prove the safety reversal still works rather than assume it.
Change three: a different address range
The camera recorder (the NVR, network video recorder, which records the four wired cameras plugged into its own ports) was the last device offline. The recorder's screen on the TV showed live video from all four cameras. The phone app said "device offline."
That split is the clue. The cameras talk to the recorder over the recorder's own internal ports, so they were fine. The recorder talks to the internet through the router, and that link had broken.
The device record's note explained it. The old gateway handed out addresses in the range 192.168.1.1 to 192.168.1.254. The installer had set the recorder to a fixed, or static, address of 192.168.1.50 so it would never move. The new router handed out addresses in 192.168.0.x. A device with a static address does not ask the router for an address; it keeps the one it was given. So the recorder was announcing itself as 192.168.1.50 on a network where nothing else lived at 192.168.1.anything. It was physically plugged in and logically on the wrong street. See related: IP Addresses and Why a Device Disappears.
Two fixes, and each has a reason:
- Change the recorder to request its address automatically (DHCP), or give it a new static address inside the new range but outside the block the router hands out. This fixes the one device.
- Change the router's address range back to 192.168.1.x. This fixes every static device at once, including any nobody remembers, but some provider-managed routers do not allow it, and it is a deeper change to the customer's network.
The tech chose the first: set the recorder to DHCP from its own menu, then, with permission, reserved its new address in the router so it would not move. The app showed the recorder online 4 minutes later, and the tech confirmed a live view on Mrs. Ortiz's phone over cellular data, not over the home Wi-Fi, which is the only way to prove remote viewing works.
The fix plan as it stood when the tech left
DEVICE BROKEN BY FIX
thermostat new name+password rename router
shutoff hub new name+password rename router
doorbell new name+password rename router
smart plug A new name+password rename router
smart plug B new name+password rename router
sprinkler ctrl WPA2/WPA3 mixed mode router -> WPA2
garage opener stale retry backoff power cycle head
camera recorder address range change DHCP + reserve
ALL 8 ONLINE, checked from phone on cellular.
The first five rows were one change. The last three were three different causes behind the same symptom, and each needed its own test to find.
Time on site, and how it was billed
Network time ran 75 minutes: 10 to inventory devices against the records, 5 for the rename, 10 waiting and checking the five that returned, 15 for the sprinkler controller, 10 for the garage opener, 25 for the recorder. None of it was the shop's own equipment failing, so all 75 minutes billed as network time under the shop's standard scope line, which Mrs. Ortiz had agreed to on the original installs. See related: Writing the Scope Line for Network and App Setup.
What the tech left behind, and why
Three things went into the customer's file before the tech left:
- Updated device records, network field rewritten for every device: ORTIZ-HOME on the new router, combined bands, WPA2 only, recorder on a reserved address in 192.168.0.x. The old values went to the job history.
- A note on the router itself, written on a label on its side: "Network name and password match old router. Do not reset without calling." A factory reset puts back the label name and password and takes the whole house offline again.
- One sentence to the customer, in writing: the next time the provider replaces the router, ask the technician to keep the same network name and password, or call us first. That one sentence prevents the next visit.
The pattern this case teaches
The tempting stopping point came at minute 25, with five of eight devices back and a clear, correct explanation in hand. Stopping there would have been reasonable-looking and wrong. A router replacement changes several things at once (the name and password, the band layout, the security mode, the address range, and any port forwarding or reservations the old unit held), and different devices depend on different ones. The correct first fix reveals which devices depended on something else. So after any router change, keep going until every device on the record is checked, from the customer's phone on cellular data, and only then call the job done.
References
- See related: The Customer Network Change Authorization SOP
- See related: IP Addresses and Why a Device Disappears
- See related: Leaving a Device Record the Next Tech Can Use
- See related: Writing the Scope Line for Network and App Setup
- Wi-Fi Alliance, published descriptions of WPA2 and WPA3 security modes